Add background sync worker and complete local-first architecture

Implements automatic background synchronization every 5 minutes:
- Worker pushes pending changes to server (PushPendingChanges)
- Worker pulls new pricelists (SyncPricelistsIfNeeded)
- Graceful shutdown with context cancellation
- Automatic online/offline detection via DB ping

New files:
- internal/services/sync/worker.go - Background sync worker
- internal/services/local_configuration.go - Local-first CRUD
- internal/localdb/converters.go - MariaDB ↔ SQLite converters

Extended sync infrastructure:
- Pending changes queue (pending_changes table)
- Push/pull sync endpoints (/api/sync/push, /pending)
- ConfigurationGetter interface for handler compatibility
- LocalConfigurationService replaces ConfigurationService

All configuration operations now run through SQLite with automatic
background sync to MariaDB when online. Phase 2.5 nearly complete.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -9,26 +9,33 @@
 ### Phase 2: Local SQLite Database ✅ DONE
 
 ### Phase 2.5: Full Offline Mode 🔶 IN PROGRESS
-Приложение должно полностью работать без MariaDB, синхронизация при восстановлении связи.
+**Local-first architecture:** приложение ВСЕГДА работает с SQLite, MariaDB только для синхронизации.
 
-**Architecture:**
+**Принцип работы:**
-- Dual-source pattern: все операции идут через unified service layer
+- ВСЕ операции (CRUD) выполняются в SQLite
-- Online: read/write MariaDB, async cache to SQLite
+- При создании конфигурации:
-- Offline: read/write SQLite, queue changes for sync
+  1. Если online → проверить новые прайслисты на сервере → скачать если есть
+  2. Далее работаем с local_pricelists (и online, и offline одинаково)
+- Background sync: push pending_changes → pull updates
+
+**DONE:**
+- ✅ Sync queue table (pending_changes) - `internal/localdb/models.go`
+- ✅ Model converters: MariaDB ↔ SQLite - `internal/localdb/converters.go`
+- ✅ LocalConfigurationService: все CRUD через SQLite - `internal/services/local_configuration.go`
+- ✅ Pre-create pricelist check: `SyncPricelistsIfNeeded()` - `internal/services/sync/service.go`
+- ✅ Push pending changes: `PushPendingChanges()` - sync service + handlers
+- ✅ Sync API endpoints: `/api/sync/push`, `/pending/count`, `/pending`
+- ✅ Integrate LocalConfigurationService in main.go (replace ConfigurationService)
+- ✅ Add routes for new sync endpoints (`/api/sync/push`, `/pending/count`, `/pending`)
+- ✅ ConfigurationGetter interface for handler compatibility
+- ✅ Background sync worker: auto-sync every 5min (push + pull) - `internal/services/sync/worker.go`
 
 **TODO:**
-- ❌ Unified repository interface (online/offline transparent switching)
+- ❌ Conflict resolution (last-write-wins or manual)
-- ❌ Sync queue table (pending_changes: entity_type, entity_uuid, operation, payload, created_at)
+- ❌ UI: pending counter in header
-- ❌ Background sync worker (push local changes when online)
+- ❌ UI: manual sync button
-- ❌ Conflict resolution (last-write-wins by updated_at, or manual)
+- ❌ UI: offline indicator (middleware already exists)
-- ❌ Initial data bootstrap (first sync downloads all needed data)
+- ❌ RefreshPrices for local mode (via local_components)
-- ❌ Handlers use context.IsOffline to choose data source
-- ❌ UI: pending changes counter, manual sync button, conflict alerts
-
-**Sync flow:**
-1. Online → Offline: continue work, changes saved locally with sync_status='pending'
-2. Offline → Online: background worker pushes pending_changes, pulls updates
-3. Conflict: if server version newer, mark as 'conflict' for manual resolution
 
 ### Phase 3: Projects and Specifications
 - qt_projects, qt_specifications tables (MariaDB)

cmd/server/main.go

@@ -108,12 +108,19 @@ func main() {
 	}
 
 	gin.SetMode(cfg.Server.Mode)
-	router, err := setupRouter(db, cfg, local, dbUserID)
+	router, syncService, err := setupRouter(db, cfg, local, dbUserID)
 	if err != nil {
 		slog.Error("failed to setup router", "error", err)
 		os.Exit(1)
 	}
 
+	// Start background sync worker
+	workerCtx, workerCancel := context.WithCancel(context.Background())
+	defer workerCancel()
+
+	syncWorker := sync.NewWorker(syncService, db, 5*time.Minute)
+	go syncWorker.Start(workerCtx)
+
 	srv := &http.Server{
 		Addr:         cfg.Address(),
 		Handler:      router,
@@ -135,6 +142,11 @@ func main() {
 
 	slog.Info("shutting down server...")
 
+	// Stop background sync worker first
+	syncWorker.Stop()
+	workerCancel()
+
+	// Then shutdown HTTP server
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
@@ -282,7 +294,7 @@ func setupDatabaseFromDSN(dsn string) (*gorm.DB, error) {
 	return db, nil
 }
 
-func setupRouter(db *gorm.DB, cfg *config.Config, local *localdb.LocalDB, dbUserID uint) (*gin.Engine, error) {
+func setupRouter(db *gorm.DB, cfg *config.Config, local *localdb.LocalDB, dbUserID uint) (*gin.Engine, *sync.Service, error) {
 	// Repositories
 	componentRepo := repository.NewComponentRepository(db)
 	categoryRepo := repository.NewCategoryRepository(db)
@@ -299,8 +311,19 @@ func setupRouter(db *gorm.DB, cfg *config.Config, local *localdb.LocalDB, dbUser
 	exportService := services.NewExportService(cfg.Export, categoryRepo)
 	alertService := alerts.NewService(alertRepo, componentRepo, priceRepo, statsRepo, cfg.Alerts, cfg.Pricing)
 	pricelistService := pricelist.NewService(db, pricelistRepo, componentRepo)
-	configService := services.NewConfigurationService(configRepo, componentRepo, quoteService)
+	syncService := sync.NewService(pricelistRepo, configRepo, local)
-	syncService := sync.NewService(pricelistRepo, local)
+
+	// isOnline function for local-first architecture
+	isOnline := func() bool {
+		sqlDB, err := db.DB()
+		if err != nil {
+			return false
+		}
+		return sqlDB.Ping() == nil
+	}
+
+	// Local-first configuration service (replaces old ConfigurationService)
+	configService := services.NewLocalConfigurationService(local, syncService, quoteService, isOnline)
 
 	// Handlers
 	componentHandler := handlers.NewComponentHandler(componentService)
@@ -313,13 +336,13 @@ func setupRouter(db *gorm.DB, cfg *config.Config, local *localdb.LocalDB, dbUser
 	// Setup handler (for reconfiguration)
 	setupHandler, err := handlers.NewSetupHandler(local, "web/templates")
 	if err != nil {
-		return nil, fmt.Errorf("creating setup handler: %w", err)
+		return nil, nil, fmt.Errorf("creating setup handler: %w", err)
 	}
 
 	// Web handler (templates)
 	webHandler, err := handlers.NewWebHandler("web/templates", componentService)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	// Router
@@ -584,10 +607,13 @@ func setupRouter(db *gorm.DB, cfg *config.Config, local *localdb.LocalDB, dbUser
 			syncAPI.POST("/components", syncHandler.SyncComponents)
 			syncAPI.POST("/pricelists", syncHandler.SyncPricelists)
 			syncAPI.POST("/all", syncHandler.SyncAll)
+			syncAPI.POST("/push", syncHandler.PushPendingChanges)
+			syncAPI.GET("/pending/count", syncHandler.GetPendingCount)
+			syncAPI.GET("/pending", syncHandler.GetPendingChanges)
 		}
 	}
 
-	return router, nil
+	return router, syncService, nil
 }
 
 func requestLogger() gin.HandlerFunc {

internal/handlers/export.go

@@ -12,13 +12,13 @@ import (
 
 type ExportHandler struct {
 	exportService    *services.ExportService
-	configService    *services.ConfigurationService
+	configService    services.ConfigurationGetter
 	componentService *services.ComponentService
 }
 
 func NewExportHandler(
 	exportService *services.ExportService,
-	configService *services.ConfigurationService,
+	configService services.ConfigurationGetter,
 	componentService *services.ComponentService,
 ) *ExportHandler {
 	return &ExportHandler{

internal/handlers/sync.go

@@ -215,3 +215,58 @@ func (h *SyncHandler) checkOnline() bool {
 
 	return true
 }
+
+// PushPendingChanges pushes all pending changes to the server
+// POST /api/sync/push
+func (h *SyncHandler) PushPendingChanges(c *gin.Context) {
+	if !h.checkOnline() {
+		c.JSON(http.StatusServiceUnavailable, gin.H{
+			"success": false,
+			"error":   "Database is offline",
+		})
+		return
+	}
+
+	startTime := time.Now()
+	pushed, err := h.syncService.PushPendingChanges()
+	if err != nil {
+		slog.Error("push pending changes failed", "error", err)
+		c.JSON(http.StatusInternalServerError, gin.H{
+			"success": false,
+			"error":   err.Error(),
+		})
+		return
+	}
+
+	c.JSON(http.StatusOK, SyncResultResponse{
+		Success:  true,
+		Message:  "Pending changes pushed successfully",
+		Synced:   pushed,
+		Duration: time.Since(startTime).String(),
+	})
+}
+
+// GetPendingCount returns the number of pending changes
+// GET /api/sync/pending/count
+func (h *SyncHandler) GetPendingCount(c *gin.Context) {
+	count := h.localDB.GetPendingCount()
+	c.JSON(http.StatusOK, gin.H{
+		"count": count,
+	})
+}
+
+// GetPendingChanges returns all pending changes
+// GET /api/sync/pending
+func (h *SyncHandler) GetPendingChanges(c *gin.Context) {
+	changes, err := h.localDB.GetPendingChanges()
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{
+			"error": err.Error(),
+		})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"changes": changes,
+	})
+}

internal/localdb/converters.go

@@ -0,0 +1,161 @@
+package localdb
+
+import (
+	"time"
+
+	"git.mchus.pro/mchus/quoteforge/internal/models"
+)
+
+// ConfigurationToLocal converts models.Configuration to LocalConfiguration
+func ConfigurationToLocal(cfg *models.Configuration) *LocalConfiguration {
+	items := make(LocalConfigItems, len(cfg.Items))
+	for i, item := range cfg.Items {
+		items[i] = LocalConfigItem{
+			LotName:   item.LotName,
+			Quantity:  item.Quantity,
+			UnitPrice: item.UnitPrice,
+		}
+	}
+
+	local := &LocalConfiguration{
+		UUID:           cfg.UUID,
+		Name:           cfg.Name,
+		Items:          items,
+		TotalPrice:     cfg.TotalPrice,
+		CustomPrice:    cfg.CustomPrice,
+		Notes:          cfg.Notes,
+		IsTemplate:     cfg.IsTemplate,
+		ServerCount:    cfg.ServerCount,
+		CreatedAt:      cfg.CreatedAt,
+		UpdatedAt:      time.Now(),
+		SyncStatus:     "pending",
+		OriginalUserID: cfg.UserID,
+	}
+
+	if cfg.ID > 0 {
+		serverID := cfg.ID
+		local.ServerID = &serverID
+	}
+
+	return local
+}
+
+// LocalToConfiguration converts LocalConfiguration to models.Configuration
+func LocalToConfiguration(local *LocalConfiguration) *models.Configuration {
+	items := make(models.ConfigItems, len(local.Items))
+	for i, item := range local.Items {
+		items[i] = models.ConfigItem{
+			LotName:   item.LotName,
+			Quantity:  item.Quantity,
+			UnitPrice: item.UnitPrice,
+		}
+	}
+
+	cfg := &models.Configuration{
+		UUID:        local.UUID,
+		UserID:      local.OriginalUserID,
+		Name:        local.Name,
+		Items:       items,
+		TotalPrice:  local.TotalPrice,
+		CustomPrice: local.CustomPrice,
+		Notes:       local.Notes,
+		IsTemplate:  local.IsTemplate,
+		ServerCount: local.ServerCount,
+		CreatedAt:   local.CreatedAt,
+	}
+
+	if local.ServerID != nil {
+		cfg.ID = *local.ServerID
+	}
+
+	return cfg
+}
+
+// PricelistToLocal converts models.Pricelist to LocalPricelist
+func PricelistToLocal(pl *models.Pricelist) *LocalPricelist {
+	name := pl.Notification
+	if name == "" {
+		name = pl.Version
+	}
+
+	return &LocalPricelist{
+		ServerID:  pl.ID,
+		Version:   pl.Version,
+		Name:      name,
+		CreatedAt: pl.CreatedAt,
+		SyncedAt:  time.Now(),
+		IsUsed:    false,
+	}
+}
+
+// LocalToPricelist converts LocalPricelist to models.Pricelist
+func LocalToPricelist(local *LocalPricelist) *models.Pricelist {
+	return &models.Pricelist{
+		ID:           local.ServerID,
+		Version:      local.Version,
+		Notification: local.Name,
+		CreatedAt:    local.CreatedAt,
+		IsActive:     true,
+	}
+}
+
+// PricelistItemToLocal converts models.PricelistItem to LocalPricelistItem
+func PricelistItemToLocal(item *models.PricelistItem, localPricelistID uint) *LocalPricelistItem {
+	return &LocalPricelistItem{
+		PricelistID: localPricelistID,
+		LotName:     item.LotName,
+		Price:       item.Price,
+	}
+}
+
+// LocalToPricelistItem converts LocalPricelistItem to models.PricelistItem
+func LocalToPricelistItem(local *LocalPricelistItem, serverPricelistID uint) *models.PricelistItem {
+	return &models.PricelistItem{
+		ID:          local.ID,
+		PricelistID: serverPricelistID,
+		LotName:     local.LotName,
+		Price:       local.Price,
+	}
+}
+
+// ComponentToLocal converts models.LotMetadata to LocalComponent
+func ComponentToLocal(meta *models.LotMetadata) *LocalComponent {
+	var lotDesc string
+	var category string
+
+	if meta.Lot != nil {
+		lotDesc = meta.Lot.LotDescription
+	}
+
+	// Extract category from lot_name (e.g., "CPU_AMD_9654" -> "CPU")
+	if len(meta.LotName) > 0 {
+		for i, ch := range meta.LotName {
+			if ch == '_' {
+				category = meta.LotName[:i]
+				break
+			}
+		}
+	}
+
+	return &LocalComponent{
+		LotName:        meta.LotName,
+		LotDescription: lotDesc,
+		Category:       category,
+		Model:          meta.Model,
+		CurrentPrice:   meta.CurrentPrice,
+		SyncedAt:       time.Now(),
+	}
+}
+
+// LocalToComponent converts LocalComponent to models.LotMetadata
+func LocalToComponent(local *LocalComponent) *models.LotMetadata {
+	return &models.LotMetadata{
+		LotName:      local.LotName,
+		Model:        local.Model,
+		CurrentPrice: local.CurrentPrice,
+		Lot: &models.Lot{
+			LotName:        local.LotName,
+			LotDescription: local.LotDescription,
+		},
+	}
+}

internal/localdb/localdb.go

@@ -56,6 +56,7 @@ func New(dbPath string) (*LocalDB, error) {
 		&LocalPricelistItem{},
 		&LocalComponent{},
 		&AppSetting{},
+		&PendingChange{},
 	); err != nil {
 		return nil, fmt.Errorf("migrating sqlite database: %w", err)
 	}
@@ -337,3 +338,73 @@ func (l *LocalDB) DeleteLocalPricelist(id uint) error {
 	// Delete pricelist
 	return l.db.Delete(&LocalPricelist{}, id).Error
 }
+
+// PendingChange methods
+
+// AddPendingChange adds a change to the sync queue
+func (l *LocalDB) AddPendingChange(entityType, entityUUID, operation, payload string) error {
+	change := PendingChange{
+		EntityType: entityType,
+		EntityUUID: entityUUID,
+		Operation:  operation,
+		Payload:    payload,
+		CreatedAt:  time.Now(),
+		Attempts:   0,
+	}
+	return l.db.Create(&change).Error
+}
+
+// GetPendingChanges returns all pending changes ordered by creation time
+func (l *LocalDB) GetPendingChanges() ([]PendingChange, error) {
+	var changes []PendingChange
+	err := l.db.Order("created_at ASC").Find(&changes).Error
+	return changes, err
+}
+
+// GetPendingChangesByEntity returns pending changes for a specific entity
+func (l *LocalDB) GetPendingChangesByEntity(entityType, entityUUID string) ([]PendingChange, error) {
+	var changes []PendingChange
+	err := l.db.Where("entity_type = ? AND entity_uuid = ?", entityType, entityUUID).
+		Order("created_at ASC").Find(&changes).Error
+	return changes, err
+}
+
+// DeletePendingChange removes a change from the sync queue after successful sync
+func (l *LocalDB) DeletePendingChange(id int64) error {
+	return l.db.Delete(&PendingChange{}, id).Error
+}
+
+// IncrementPendingChangeAttempts updates the attempt counter and last error
+func (l *LocalDB) IncrementPendingChangeAttempts(id int64, errorMsg string) error {
+	return l.db.Model(&PendingChange{}).Where("id = ?", id).Updates(map[string]interface{}{
+		"attempts":   gorm.Expr("attempts + 1"),
+		"last_error": errorMsg,
+	}).Error
+}
+
+// CountPendingChanges returns the total number of pending changes
+func (l *LocalDB) CountPendingChanges() int64 {
+	var count int64
+	l.db.Model(&PendingChange{}).Count(&count)
+	return count
+}
+
+// CountPendingChangesByType returns the number of pending changes by entity type
+func (l *LocalDB) CountPendingChangesByType(entityType string) int64 {
+	var count int64
+	l.db.Model(&PendingChange{}).Where("entity_type = ?", entityType).Count(&count)
+	return count
+}
+
+// MarkChangesSynced marks multiple pending changes as synced by deleting them
+func (l *LocalDB) MarkChangesSynced(ids []int64) error {
+	if len(ids) == 0 {
+		return nil
+	}
+	return l.db.Where("id IN ?", ids).Delete(&PendingChange{}).Error
+}
+
+// GetPendingCount returns the total number of pending changes (alias for CountPendingChanges)
+func (l *LocalDB) GetPendingCount() int64 {
+	return l.CountPendingChanges()
+}

internal/localdb/models.go

@@ -120,3 +120,19 @@ type LocalComponent struct {
 func (LocalComponent) TableName() string {
 	return "local_components"
 }
+
+// PendingChange stores changes that need to be synced to the server
+type PendingChange struct {
+	ID         int64     `gorm:"primaryKey;autoIncrement" json:"id"`
+	EntityType string    `gorm:"not null;index" json:"entity_type"` // "configuration", "project", "specification"
+	EntityUUID string    `gorm:"not null;index" json:"entity_uuid"`
+	Operation  string    `gorm:"not null" json:"operation"` // "create", "update", "delete"
+	Payload    string    `gorm:"type:text" json:"payload"`  // JSON snapshot of the entity
+	CreatedAt  time.Time `gorm:"not null" json:"created_at"`
+	Attempts   int       `gorm:"default:0" json:"attempts"` // Retry count for sync
+	LastError  string    `gorm:"type:text" json:"last_error,omitempty"`
+}
+
+func (PendingChange) TableName() string {
+	return "pending_changes"
+}

internal/services/configuration.go

@@ -14,6 +14,12 @@ var (
 	ErrConfigForbidden  = errors.New("access to configuration forbidden")
 )
 
+// ConfigurationGetter is an interface for services that can retrieve configurations
+// Used by handlers to work with both ConfigurationService and LocalConfigurationService
+type ConfigurationGetter interface {
+	GetByUUID(uuid string, userID uint) (*models.Configuration, error)
+}
+
 type ConfigurationService struct {
 	configRepo    *repository.ConfigurationRepository
 	componentRepo *repository.ComponentRepository

internal/services/local_configuration.go

@@ -0,0 +1,509 @@
+package services
+
+import (
+	"encoding/json"
+	"errors"
+	"time"
+
+	"github.com/google/uuid"
+	"git.mchus.pro/mchus/quoteforge/internal/localdb"
+	"git.mchus.pro/mchus/quoteforge/internal/models"
+	"git.mchus.pro/mchus/quoteforge/internal/services/sync"
+)
+
+// LocalConfigurationService handles configurations in local-first mode
+// All operations go through SQLite, MariaDB is used only for sync
+type LocalConfigurationService struct {
+	localDB      *localdb.LocalDB
+	syncService  *sync.Service
+	quoteService *QuoteService
+	isOnline     func() bool // Function to check if we're online
+}
+
+// NewLocalConfigurationService creates a new local-first configuration service
+func NewLocalConfigurationService(
+	localDB *localdb.LocalDB,
+	syncService *sync.Service,
+	quoteService *QuoteService,
+	isOnline func() bool,
+) *LocalConfigurationService {
+	return &LocalConfigurationService{
+		localDB:      localDB,
+		syncService:  syncService,
+		quoteService: quoteService,
+		isOnline:     isOnline,
+	}
+}
+
+// Create creates a new configuration in local SQLite and queues it for sync
+func (s *LocalConfigurationService) Create(userID uint, req *CreateConfigRequest) (*models.Configuration, error) {
+	// If online, check for new pricelists first
+	if s.isOnline() {
+		if err := s.syncService.SyncPricelistsIfNeeded(); err != nil {
+			// Log but don't fail - we can still use local pricelists
+		}
+	}
+
+	total := req.Items.Total()
+	if req.ServerCount > 1 {
+		total *= float64(req.ServerCount)
+	}
+
+	cfg := &models.Configuration{
+		UUID:        uuid.New().String(),
+		UserID:      userID,
+		Name:        req.Name,
+		Items:       req.Items,
+		TotalPrice:  &total,
+		CustomPrice: req.CustomPrice,
+		Notes:       req.Notes,
+		IsTemplate:  req.IsTemplate,
+		ServerCount: req.ServerCount,
+		CreatedAt:   time.Now(),
+	}
+
+	// Convert to local model
+	localCfg := localdb.ConfigurationToLocal(cfg)
+
+	// Save to local SQLite
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	// Add to pending sync queue
+	payload, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", cfg.UUID, "create", string(payload)); err != nil {
+		return nil, err
+	}
+
+	// Record usage stats
+	_ = s.quoteService.RecordUsage(req.Items)
+
+	return cfg, nil
+}
+
+// GetByUUID returns a configuration from local SQLite
+func (s *LocalConfigurationService) GetByUUID(uuid string, userID uint) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+
+	// Convert to models.Configuration
+	cfg := localdb.LocalToConfiguration(localCfg)
+
+	// Allow access if user owns config or it's a template
+	if cfg.UserID != userID && !cfg.IsTemplate {
+		return nil, ErrConfigForbidden
+	}
+
+	return cfg, nil
+}
+
+// Update updates a configuration in local SQLite and queues it for sync
+func (s *LocalConfigurationService) Update(uuid string, userID uint, req *CreateConfigRequest) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+
+	if localCfg.OriginalUserID != userID {
+		return nil, ErrConfigForbidden
+	}
+
+	total := req.Items.Total()
+	if req.ServerCount > 1 {
+		total *= float64(req.ServerCount)
+	}
+
+	// Update fields
+	localCfg.Name = req.Name
+	localCfg.Items = localdb.LocalConfigItems{}
+	for _, item := range req.Items {
+		localCfg.Items = append(localCfg.Items, localdb.LocalConfigItem{
+			LotName:   item.LotName,
+			Quantity:  item.Quantity,
+			UnitPrice: item.UnitPrice,
+		})
+	}
+	localCfg.TotalPrice = &total
+	localCfg.CustomPrice = req.CustomPrice
+	localCfg.Notes = req.Notes
+	localCfg.IsTemplate = req.IsTemplate
+	localCfg.ServerCount = req.ServerCount
+	localCfg.UpdatedAt = time.Now()
+	localCfg.SyncStatus = "pending"
+
+	// Save to local SQLite
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	// Add to pending sync queue
+	cfg := localdb.LocalToConfiguration(localCfg)
+	payload, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", uuid, "update", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+// Delete deletes a configuration from local SQLite and queues it for sync
+func (s *LocalConfigurationService) Delete(uuid string, userID uint) error {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return ErrConfigNotFound
+	}
+
+	if localCfg.OriginalUserID != userID {
+		return ErrConfigForbidden
+	}
+
+	// Delete from local SQLite
+	if err := s.localDB.DeleteConfiguration(uuid); err != nil {
+		return err
+	}
+
+	// Add to pending sync queue
+	if err := s.localDB.AddPendingChange("configuration", uuid, "delete", ""); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Rename renames a configuration
+func (s *LocalConfigurationService) Rename(uuid string, userID uint, newName string) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+
+	if localCfg.OriginalUserID != userID {
+		return nil, ErrConfigForbidden
+	}
+
+	localCfg.Name = newName
+	localCfg.UpdatedAt = time.Now()
+	localCfg.SyncStatus = "pending"
+
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	// Add to pending sync queue
+	cfg := localdb.LocalToConfiguration(localCfg)
+	payload, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", uuid, "update", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+// Clone clones a configuration
+func (s *LocalConfigurationService) Clone(configUUID string, userID uint, newName string) (*models.Configuration, error) {
+	original, err := s.GetByUUID(configUUID, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	total := original.Items.Total()
+	if original.ServerCount > 1 {
+		total *= float64(original.ServerCount)
+	}
+
+	clone := &models.Configuration{
+		UUID:        uuid.New().String(),
+		UserID:      userID,
+		Name:        newName,
+		Items:       original.Items,
+		TotalPrice:  &total,
+		CustomPrice: original.CustomPrice,
+		Notes:       original.Notes,
+		IsTemplate:  false,
+		ServerCount: original.ServerCount,
+		CreatedAt:   time.Now(),
+	}
+
+	localCfg := localdb.ConfigurationToLocal(clone)
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	// Add to pending sync queue
+	payload, err := json.Marshal(clone)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", clone.UUID, "create", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return clone, nil
+}
+
+// ListByUser returns all configurations for a user from local SQLite
+func (s *LocalConfigurationService) ListByUser(userID uint, page, perPage int) ([]models.Configuration, int64, error) {
+	// Get all local configurations
+	localConfigs, err := s.localDB.GetConfigurations()
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// Filter by user
+	var userConfigs []models.Configuration
+	for _, lc := range localConfigs {
+		if lc.OriginalUserID == userID || lc.IsTemplate {
+			userConfigs = append(userConfigs, *localdb.LocalToConfiguration(&lc))
+		}
+	}
+
+	total := int64(len(userConfigs))
+
+	// Apply pagination
+	if page < 1 {
+		page = 1
+	}
+	if perPage < 1 || perPage > 100 {
+		perPage = 20
+	}
+	offset := (page - 1) * perPage
+
+	start := offset
+	if start > len(userConfigs) {
+		start = len(userConfigs)
+	}
+	end := start + perPage
+	if end > len(userConfigs) {
+		end = len(userConfigs)
+	}
+
+	return userConfigs[start:end], total, nil
+}
+
+// RefreshPrices updates all component prices in the configuration
+func (s *LocalConfigurationService) RefreshPrices(uuid string, userID uint) (*models.Configuration, error) {
+	// This requires access to component prices from local cache
+	// For now, return error as we need to implement component price lookup from local cache
+	return nil, errors.New("refresh prices not yet implemented for local-first mode")
+}
+
+// GetByUUIDNoAuth returns configuration without ownership check
+func (s *LocalConfigurationService) GetByUUIDNoAuth(uuid string) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+	return localdb.LocalToConfiguration(localCfg), nil
+}
+
+// UpdateNoAuth updates configuration without ownership check
+func (s *LocalConfigurationService) UpdateNoAuth(uuid string, req *CreateConfigRequest) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+
+	total := req.Items.Total()
+	if req.ServerCount > 1 {
+		total *= float64(req.ServerCount)
+	}
+
+	localCfg.Name = req.Name
+	localCfg.Items = localdb.LocalConfigItems{}
+	for _, item := range req.Items {
+		localCfg.Items = append(localCfg.Items, localdb.LocalConfigItem{
+			LotName:   item.LotName,
+			Quantity:  item.Quantity,
+			UnitPrice: item.UnitPrice,
+		})
+	}
+	localCfg.TotalPrice = &total
+	localCfg.CustomPrice = req.CustomPrice
+	localCfg.Notes = req.Notes
+	localCfg.IsTemplate = req.IsTemplate
+	localCfg.ServerCount = req.ServerCount
+	localCfg.UpdatedAt = time.Now()
+	localCfg.SyncStatus = "pending"
+
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	cfg := localdb.LocalToConfiguration(localCfg)
+	payload, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", uuid, "update", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+// DeleteNoAuth deletes configuration without ownership check
+func (s *LocalConfigurationService) DeleteNoAuth(uuid string) error {
+	if err := s.localDB.DeleteConfiguration(uuid); err != nil {
+		return err
+	}
+	return s.localDB.AddPendingChange("configuration", uuid, "delete", "")
+}
+
+// RenameNoAuth renames configuration without ownership check
+func (s *LocalConfigurationService) RenameNoAuth(uuid string, newName string) (*models.Configuration, error) {
+	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
+	if err != nil {
+		return nil, ErrConfigNotFound
+	}
+
+	localCfg.Name = newName
+	localCfg.UpdatedAt = time.Now()
+	localCfg.SyncStatus = "pending"
+
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	cfg := localdb.LocalToConfiguration(localCfg)
+	payload, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", uuid, "update", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+// CloneNoAuth clones configuration without ownership check
+func (s *LocalConfigurationService) CloneNoAuth(configUUID string, newName string, userID uint) (*models.Configuration, error) {
+	original, err := s.GetByUUIDNoAuth(configUUID)
+	if err != nil {
+		return nil, err
+	}
+
+	total := original.Items.Total()
+	if original.ServerCount > 1 {
+		total *= float64(original.ServerCount)
+	}
+
+	clone := &models.Configuration{
+		UUID:        uuid.New().String(),
+		UserID:      userID,
+		Name:        newName,
+		Items:       original.Items,
+		TotalPrice:  &total,
+		CustomPrice: original.CustomPrice,
+		Notes:       original.Notes,
+		IsTemplate:  false,
+		ServerCount: original.ServerCount,
+		CreatedAt:   time.Now(),
+	}
+
+	localCfg := localdb.ConfigurationToLocal(clone)
+	if err := s.localDB.SaveConfiguration(localCfg); err != nil {
+		return nil, err
+	}
+
+	payload, err := json.Marshal(clone)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.localDB.AddPendingChange("configuration", clone.UUID, "create", string(payload)); err != nil {
+		return nil, err
+	}
+
+	return clone, nil
+}
+
+// ListAll returns all configurations without user filter
+func (s *LocalConfigurationService) ListAll(page, perPage int) ([]models.Configuration, int64, error) {
+	localConfigs, err := s.localDB.GetConfigurations()
+	if err != nil {
+		return nil, 0, err
+	}
+
+	configs := make([]models.Configuration, len(localConfigs))
+	for i, lc := range localConfigs {
+		configs[i] = *localdb.LocalToConfiguration(&lc)
+	}
+
+	total := int64(len(configs))
+
+	// Apply pagination
+	if page < 1 {
+		page = 1
+	}
+	if perPage < 1 || perPage > 100 {
+		perPage = 20
+	}
+	offset := (page - 1) * perPage
+
+	start := offset
+	if start > len(configs) {
+		start = len(configs)
+	}
+	end := start + perPage
+	if end > len(configs) {
+		end = len(configs)
+	}
+
+	return configs[start:end], total, nil
+}
+
+// ListTemplates returns all template configurations
+func (s *LocalConfigurationService) ListTemplates(page, perPage int) ([]models.Configuration, int64, error) {
+	localConfigs, err := s.localDB.GetConfigurations()
+	if err != nil {
+		return nil, 0, err
+	}
+
+	var templates []models.Configuration
+	for _, lc := range localConfigs {
+		if lc.IsTemplate {
+			templates = append(templates, *localdb.LocalToConfiguration(&lc))
+		}
+	}
+
+	total := int64(len(templates))
+
+	// Apply pagination
+	if page < 1 {
+		page = 1
+	}
+	if perPage < 1 || perPage > 100 {
+		perPage = 20
+	}
+	offset := (page - 1) * perPage
+
+	start := offset
+	if start > len(templates) {
+		start = len(templates)
+	}
+	end := start + perPage
+	if end > len(templates) {
+		end = len(templates)
+	}
+
+	return templates[start:end], total, nil
+}
+
+// RefreshPricesNoAuth updates all component prices in the configuration without ownership check
+func (s *LocalConfigurationService) RefreshPricesNoAuth(uuid string) (*models.Configuration, error) {
+	// This requires access to component prices from local cache
+	// For now, return error as we need to implement component price lookup from local cache
+	return nil, errors.New("refresh prices not yet implemented for local-first mode")
+}

internal/services/sync/service.go

@@ -1,24 +1,28 @@
 package sync
 
 import (
+	"encoding/json"
 	"fmt"
 	"log/slog"
 	"time"
 
 	"git.mchus.pro/mchus/quoteforge/internal/localdb"
+	"git.mchus.pro/mchus/quoteforge/internal/models"
 	"git.mchus.pro/mchus/quoteforge/internal/repository"
 )
 
 // Service handles synchronization between MariaDB and local SQLite
 type Service struct {
 	pricelistRepo *repository.PricelistRepository
+	configRepo    *repository.ConfigurationRepository
 	localDB       *localdb.LocalDB
 }
 
 // NewService creates a new sync service
-func NewService(pricelistRepo *repository.PricelistRepository, localDB *localdb.LocalDB) *Service {
+func NewService(pricelistRepo *repository.PricelistRepository, configRepo *repository.ConfigurationRepository, localDB *localdb.LocalDB) *Service {
 	return &Service{
 		pricelistRepo: pricelistRepo,
+		configRepo:    configRepo,
 		localDB:       localDB,
 	}
 }
@@ -213,3 +217,157 @@ func (s *Service) GetPricelistForOffline(serverPricelistID uint) (*localdb.Local
 
 	return localPL, nil
 }
+
+// SyncPricelistsIfNeeded checks for new pricelists and syncs if needed
+// This should be called before creating a new configuration when online
+func (s *Service) SyncPricelistsIfNeeded() error {
+	needSync, err := s.NeedSync()
+	if err != nil {
+		slog.Warn("failed to check if sync needed", "error", err)
+		return nil // Don't fail on check error
+	}
+
+	if !needSync {
+		slog.Debug("pricelists are up to date, no sync needed")
+		return nil
+	}
+
+	slog.Info("new pricelists detected, syncing...")
+	_, err = s.SyncPricelists()
+	if err != nil {
+		return fmt.Errorf("syncing pricelists: %w", err)
+	}
+
+	return nil
+}
+
+// PushPendingChanges pushes all pending changes to the server
+func (s *Service) PushPendingChanges() (int, error) {
+	changes, err := s.localDB.GetPendingChanges()
+	if err != nil {
+		return 0, fmt.Errorf("getting pending changes: %w", err)
+	}
+
+	if len(changes) == 0 {
+		slog.Debug("no pending changes to push")
+		return 0, nil
+	}
+
+	slog.Info("pushing pending changes", "count", len(changes))
+	pushed := 0
+	var syncedIDs []int64
+
+	for _, change := range changes {
+		err := s.pushSingleChange(&change)
+		if err != nil {
+			slog.Warn("failed to push change", "id", change.ID, "type", change.EntityType, "operation", change.Operation, "error", err)
+			// Increment attempts
+			s.localDB.IncrementPendingChangeAttempts(change.ID, err.Error())
+			continue
+		}
+
+		syncedIDs = append(syncedIDs, change.ID)
+		pushed++
+	}
+
+	// Mark synced changes as complete by deleting them
+	if len(syncedIDs) > 0 {
+		if err := s.localDB.MarkChangesSynced(syncedIDs); err != nil {
+			slog.Error("failed to mark changes as synced", "error", err)
+		}
+	}
+
+	slog.Info("pending changes pushed", "pushed", pushed, "failed", len(changes)-pushed)
+	return pushed, nil
+}
+
+// pushSingleChange pushes a single pending change to the server
+func (s *Service) pushSingleChange(change *localdb.PendingChange) error {
+	switch change.EntityType {
+	case "configuration":
+		return s.pushConfigurationChange(change)
+	default:
+		return fmt.Errorf("unknown entity type: %s", change.EntityType)
+	}
+}
+
+// pushConfigurationChange pushes a configuration change to the server
+func (s *Service) pushConfigurationChange(change *localdb.PendingChange) error {
+	switch change.Operation {
+	case "create":
+		return s.pushConfigurationCreate(change)
+	case "update":
+		return s.pushConfigurationUpdate(change)
+	case "delete":
+		return s.pushConfigurationDelete(change)
+	default:
+		return fmt.Errorf("unknown operation: %s", change.Operation)
+	}
+}
+
+// pushConfigurationCreate creates a configuration on the server
+func (s *Service) pushConfigurationCreate(change *localdb.PendingChange) error {
+	var cfg models.Configuration
+	if err := json.Unmarshal([]byte(change.Payload), &cfg); err != nil {
+		return fmt.Errorf("unmarshaling configuration: %w", err)
+	}
+
+	// Create on server
+	if err := s.configRepo.Create(&cfg); err != nil {
+		return fmt.Errorf("creating configuration on server: %w", err)
+	}
+
+	// Update local configuration with server ID
+	localCfg, err := s.localDB.GetConfigurationByUUID(cfg.UUID)
+	if err == nil {
+		serverID := cfg.ID
+		localCfg.ServerID = &serverID
+		localCfg.SyncStatus = "synced"
+		s.localDB.SaveConfiguration(localCfg)
+	}
+
+	slog.Info("configuration created on server", "uuid", cfg.UUID, "server_id", cfg.ID)
+	return nil
+}
+
+// pushConfigurationUpdate updates a configuration on the server
+func (s *Service) pushConfigurationUpdate(change *localdb.PendingChange) error {
+	var cfg models.Configuration
+	if err := json.Unmarshal([]byte(change.Payload), &cfg); err != nil {
+		return fmt.Errorf("unmarshaling configuration: %w", err)
+	}
+
+	// Update on server
+	if err := s.configRepo.Update(&cfg); err != nil {
+		return fmt.Errorf("updating configuration on server: %w", err)
+	}
+
+	// Update local sync status
+	localCfg, err := s.localDB.GetConfigurationByUUID(cfg.UUID)
+	if err == nil {
+		localCfg.SyncStatus = "synced"
+		s.localDB.SaveConfiguration(localCfg)
+	}
+
+	slog.Info("configuration updated on server", "uuid", cfg.UUID)
+	return nil
+}
+
+// pushConfigurationDelete deletes a configuration from the server
+func (s *Service) pushConfigurationDelete(change *localdb.PendingChange) error {
+	// Get the configuration from server by UUID to get the ID
+	cfg, err := s.configRepo.GetByUUID(change.EntityUUID)
+	if err != nil {
+		// Already deleted or not found, consider it successful
+		slog.Warn("configuration not found on server, considering delete successful", "uuid", change.EntityUUID)
+		return nil
+	}
+
+	// Delete from server
+	if err := s.configRepo.Delete(cfg.ID); err != nil {
+		return fmt.Errorf("deleting configuration from server: %w", err)
+	}
+
+	slog.Info("configuration deleted from server", "uuid", change.EntityUUID)
+	return nil
+}

internal/services/sync/worker.go

@@ -0,0 +1,95 @@
+package sync
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"gorm.io/gorm"
+)
+
+// Worker performs background synchronization at regular intervals
+type Worker struct {
+	service  *Service
+	db       *gorm.DB
+	interval time.Duration
+	logger   *slog.Logger
+	stopCh   chan struct{}
+}
+
+// NewWorker creates a new background sync worker
+func NewWorker(service *Service, db *gorm.DB, interval time.Duration) *Worker {
+	return &Worker{
+		service:  service,
+		db:       db,
+		interval: interval,
+		logger:   slog.Default(),
+		stopCh:   make(chan struct{}),
+	}
+}
+
+// isOnline checks if the database connection is available
+func (w *Worker) isOnline() bool {
+	sqlDB, err := w.db.DB()
+	if err != nil {
+		return false
+	}
+	return sqlDB.Ping() == nil
+}
+
+// Start begins the background sync loop in a goroutine
+func (w *Worker) Start(ctx context.Context) {
+	w.logger.Info("starting background sync worker", "interval", w.interval)
+
+	ticker := time.NewTicker(w.interval)
+	defer ticker.Stop()
+
+	// Run once immediately
+	w.runSync()
+
+	for {
+		select {
+		case <-ctx.Done():
+			w.logger.Info("background sync worker stopped by context")
+			return
+		case <-w.stopCh:
+			w.logger.Info("background sync worker stopped")
+			return
+		case <-ticker.C:
+			w.runSync()
+		}
+	}
+}
+
+// Stop gracefully stops the worker
+func (w *Worker) Stop() {
+	w.logger.Info("stopping background sync worker")
+	close(w.stopCh)
+}
+
+// runSync performs a single sync iteration
+func (w *Worker) runSync() {
+	// Check if online
+	if !w.isOnline() {
+		w.logger.Debug("offline, skipping background sync")
+		return
+	}
+
+	w.logger.Debug("running background sync")
+
+	// Push pending changes first
+	pushed, err := w.service.PushPendingChanges()
+	if err != nil {
+		w.logger.Warn("failed to push pending changes", "error", err)
+	} else if pushed > 0 {
+		w.logger.Info("pushed pending changes", "count", pushed)
+	}
+
+	// Then check for new pricelists
+	err = w.service.SyncPricelistsIfNeeded()
+	if err != nil {
+		w.logger.Warn("failed to sync pricelists", "error", err)
+	}
+
+	w.logger.Debug("background sync completed")
+}