Add Phase 2: Local SQLite database with sync functionality

Implements complete offline-first architecture with SQLite caching and MariaDB synchronization.

Key features:
- Local SQLite database for offline operation (data/quoteforge.db)
- Connection settings with encrypted credentials
- Component and pricelist caching with auto-sync
- Sync API endpoints (/api/sync/status, /components, /pricelists, /all)
- Real-time sync status indicator in UI with auto-refresh
- Offline mode detection middleware
- Migration tool for database initialization
- Setup wizard for initial configuration

New components:
- internal/localdb: SQLite repository layer (components, pricelists, sync)
- internal/services/sync: Synchronization service
- internal/handlers/sync: Sync API handlers
- internal/handlers/setup: Setup wizard handlers
- internal/middleware/offline: Offline detection
- cmd/migrate: Database migration tool

UI improvements:
- Setup page for database configuration
- Sync status indicator with online/offline detection
- Warning icons for pending synchronization
- Auto-refresh every 30 seconds

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

internal/services/pricelist/service.go

@@ -0,0 +1,156 @@
+package pricelist
+
+import (
+	"fmt"
+	"log/slog"
+	"time"
+
+	"git.mchus.pro/mchus/quoteforge/internal/models"
+	"git.mchus.pro/mchus/quoteforge/internal/repository"
+	"gorm.io/gorm"
+)
+
+type Service struct {
+	repo          *repository.PricelistRepository
+	componentRepo *repository.ComponentRepository
+	db            *gorm.DB
+}
+
+func NewService(db *gorm.DB, repo *repository.PricelistRepository, componentRepo *repository.ComponentRepository) *Service {
+	return &Service{
+		repo:          repo,
+		componentRepo: componentRepo,
+		db:            db,
+	}
+}
+
+// CreateFromCurrentPrices creates a new pricelist by taking a snapshot of current prices
+func (s *Service) CreateFromCurrentPrices(createdBy string) (*models.Pricelist, error) {
+	version, err := s.repo.GenerateVersion()
+	if err != nil {
+		return nil, fmt.Errorf("generating version: %w", err)
+	}
+
+	expiresAt := time.Now().AddDate(1, 0, 0) // +1 year
+
+	pricelist := &models.Pricelist{
+		Version:   version,
+		CreatedBy: createdBy,
+		IsActive:  true,
+		ExpiresAt: &expiresAt,
+	}
+
+	if err := s.repo.Create(pricelist); err != nil {
+		return nil, fmt.Errorf("creating pricelist: %w", err)
+	}
+
+	// Get all components with prices from qt_lot_metadata
+	var metadata []models.LotMetadata
+	if err := s.db.Where("current_price IS NOT NULL AND current_price > 0").Find(&metadata).Error; err != nil {
+		return nil, fmt.Errorf("getting lot metadata: %w", err)
+	}
+
+	// Create pricelist items with all price settings
+	items := make([]models.PricelistItem, 0, len(metadata))
+	for _, m := range metadata {
+		if m.CurrentPrice == nil || *m.CurrentPrice <= 0 {
+			continue
+		}
+		items = append(items, models.PricelistItem{
+			PricelistID:      pricelist.ID,
+			LotName:          m.LotName,
+			Price:            *m.CurrentPrice,
+			PriceMethod:      string(m.PriceMethod),
+			PricePeriodDays:  m.PricePeriodDays,
+			PriceCoefficient: m.PriceCoefficient,
+			ManualPrice:      m.ManualPrice,
+			MetaPrices:       m.MetaPrices,
+		})
+	}
+
+	if err := s.repo.CreateItems(items); err != nil {
+		// Clean up the pricelist if items creation fails
+		s.repo.Delete(pricelist.ID)
+		return nil, fmt.Errorf("creating pricelist items: %w", err)
+	}
+
+	pricelist.ItemCount = len(items)
+
+	slog.Info("pricelist created",
+		"id", pricelist.ID,
+		"version", pricelist.Version,
+		"items", len(items),
+		"created_by", createdBy,
+	)
+
+	return pricelist, nil
+}
+
+// List returns pricelists with pagination
+func (s *Service) List(page, perPage int) ([]models.PricelistSummary, int64, error) {
+	if page < 1 {
+		page = 1
+	}
+	if perPage < 1 {
+		perPage = 20
+	}
+	offset := (page - 1) * perPage
+	return s.repo.List(offset, perPage)
+}
+
+// GetByID returns a pricelist by ID
+func (s *Service) GetByID(id uint) (*models.Pricelist, error) {
+	return s.repo.GetByID(id)
+}
+
+// GetItems returns pricelist items with pagination
+func (s *Service) GetItems(pricelistID uint, page, perPage int, search string) ([]models.PricelistItem, int64, error) {
+	if page < 1 {
+		page = 1
+	}
+	if perPage < 1 {
+		perPage = 50
+	}
+	offset := (page - 1) * perPage
+	return s.repo.GetItems(pricelistID, offset, perPage, search)
+}
+
+// Delete deletes a pricelist by ID
+func (s *Service) Delete(id uint) error {
+	return s.repo.Delete(id)
+}
+
+// CanWrite returns true if the user can create pricelists
+func (s *Service) CanWrite() bool {
+	return s.repo.CanWrite()
+}
+
+// CanWriteDebug returns write permission status with debug info
+func (s *Service) CanWriteDebug() (bool, string) {
+	return s.repo.CanWriteDebug()
+}
+
+// GetLatestActive returns the most recent active pricelist
+func (s *Service) GetLatestActive() (*models.Pricelist, error) {
+	return s.repo.GetLatestActive()
+}
+
+// CleanupExpired deletes expired and unused pricelists
+func (s *Service) CleanupExpired() (int, error) {
+	expired, err := s.repo.GetExpiredUnused()
+	if err != nil {
+		return 0, err
+	}
+
+	deleted := 0
+	for _, pl := range expired {
+		if err := s.repo.Delete(pl.ID); err != nil {
+			slog.Warn("failed to delete expired pricelist", "id", pl.ID, "error", err)
+			continue
+		}
+		deleted++
+	}
+
+	slog.Info("cleaned up expired pricelists", "deleted", deleted)
+	return deleted, nil
+}