Add configuration revisions system and project variant deletion

Features:
- Configuration versioning: immutable snapshots in local_configuration_versions
- Revisions UI: /configs/:uuid/revisions page to view version history
- Clone from version: ability to clone configuration from specific revision
- Project variant deletion: DELETE /api/projects/:uuid endpoint
- Updated CLAUDE.md with new architecture details and endpoints

Architecture updates:
- local_configuration_versions table for immutable snapshots
- Version tracking on each configuration save
- Rollback capability to previous versions
- Variant deletion with main variant protection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/services/local_configuration.go

@@ -442,14 +442,14 @@ func (s *LocalConfigurationService) RefreshPrices(uuid string, ownerUsername str
 
 // GetByUUIDNoAuth returns configuration without ownership check
 func (s *LocalConfigurationService) GetByUUIDNoAuth(uuid string) (*models.Configuration, error) {
-	localCfg, err := s.localDB.GetConfigurationByUUID(uuid)
-	if err != nil {
+	var localCfg localdb.LocalConfiguration
+	if err := s.localDB.DB().Preload("CurrentVersion").Where("uuid = ?", uuid).First(&localCfg).Error; err != nil {
 		return nil, ErrConfigNotFound
 	}
 	if !localCfg.IsActive {
 		return nil, ErrConfigNotFound
 	}
-	return localdb.LocalToConfiguration(localCfg), nil
+	return localdb.LocalToConfiguration(&localCfg), nil
 }
 
 // UpdateNoAuth updates configuration without ownership check
@@ -571,10 +571,30 @@ func (s *LocalConfigurationService) CloneNoAuth(configUUID string, newName strin
 }
 
 func (s *LocalConfigurationService) CloneNoAuthToProject(configUUID string, newName string, ownerUsername string, projectUUID *string) (*models.Configuration, error) {
+	return s.CloneNoAuthToProjectFromVersion(configUUID, newName, ownerUsername, projectUUID, 0)
+}
+
+func (s *LocalConfigurationService) CloneNoAuthToProjectFromVersion(configUUID string, newName string, ownerUsername string, projectUUID *string, fromVersion int) (*models.Configuration, error) {
 	original, err := s.GetByUUIDNoAuth(configUUID)
 	if err != nil {
 		return nil, err
 	}
+
+	// If fromVersion specified, use snapshot from that version
+	if fromVersion > 0 {
+		version, vErr := s.GetVersion(configUUID, fromVersion)
+		if vErr != nil {
+			return nil, vErr
+		}
+		snapshot, decErr := s.decodeConfigurationSnapshot(version.Data)
+		if decErr != nil {
+			return nil, fmt.Errorf("decode version snapshot for clone: %w", decErr)
+		}
+		snapshotCfg := localdb.LocalToConfiguration(snapshot)
+		original = snapshotCfg
+		original.UUID = configUUID // preserve original UUID for project resolution
+	}
+
 	resolvedProjectUUID := original.ProjectUUID
 	if projectUUID != nil {
 		resolvedProjectUUID, err = s.resolveProjectUUID(ownerUsername, projectUUID)
@@ -896,6 +916,7 @@ func (s *LocalConfigurationService) createWithVersion(localCfg *localdb.LocalCon
 			return fmt.Errorf("set current version id: %w", err)
 		}
 		localCfg.CurrentVersionID = &version.ID
+		localCfg.CurrentVersion = version
 
 		if err := s.enqueueConfigurationPendingChangeTx(tx, localCfg, "create", version, createdBy); err != nil {
 			return fmt.Errorf("enqueue create pending change: %w", err)
@@ -937,6 +958,7 @@ func (s *LocalConfigurationService) saveWithVersionAndPending(localCfg *localdb.
 			return fmt.Errorf("update current version id: %w", err)
 		}
 		localCfg.CurrentVersionID = &version.ID
+		localCfg.CurrentVersion = version
 
 		cfg = localdb.LocalToConfiguration(localCfg)
 		if err := s.enqueueConfigurationPendingChangeTx(tx, localCfg, operation, version, createdBy); err != nil {

internal/services/project.go

@@ -16,9 +16,10 @@ import (
 )
 
 var (
-	ErrProjectNotFound   = errors.New("project not found")
-	ErrProjectForbidden  = errors.New("access to project forbidden")
-	ErrProjectCodeExists = errors.New("project code and variant already exist")
+	ErrProjectNotFound          = errors.New("project not found")
+	ErrProjectForbidden         = errors.New("access to project forbidden")
+	ErrProjectCodeExists        = errors.New("project code and variant already exist")
+	ErrCannotDeleteMainVariant  = errors.New("cannot delete main variant")
 )
 
 type ProjectService struct {
@@ -173,6 +174,17 @@ func (s *ProjectService) Reactivate(projectUUID, ownerUsername string) error {
 	return s.setProjectActive(projectUUID, ownerUsername, true)
 }
 
+func (s *ProjectService) DeleteVariant(projectUUID, ownerUsername string) error {
+	localProject, err := s.localDB.GetProjectByUUID(projectUUID)
+	if err != nil {
+		return ErrProjectNotFound
+	}
+	if strings.TrimSpace(localProject.Variant) == "" {
+		return ErrCannotDeleteMainVariant
+	}
+	return s.setProjectActive(projectUUID, ownerUsername, false)
+}
+
 func (s *ProjectService) setProjectActive(projectUUID, ownerUsername string, isActive bool) error {
 	return s.localDB.DB().Transaction(func(tx *gorm.DB) error {
 		var project localdb.LocalProject
@@ -263,8 +275,8 @@ func (s *ProjectService) ListConfigurations(projectUUID, ownerUsername, status s
 		}, nil
 	}
 
-	localConfigs, err := s.localDB.GetConfigurations()
-	if err != nil {
+	var localConfigs []localdb.LocalConfiguration
+	if err := s.localDB.DB().Preload("CurrentVersion").Order("created_at DESC").Find(&localConfigs).Error; err != nil {
 		return nil, err
 	}