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/localdb/converters.go

@@ -91,6 +91,9 @@ func LocalToConfiguration(local *LocalConfiguration) *models.Configuration {
 		userID := local.OriginalUserID
 		cfg.UserID = &userID
 	}
+	if local.CurrentVersion != nil {
+		cfg.CurrentVersionNo = local.CurrentVersion.VersionNo
+	}
 
 	return cfg
 }