feat: context menus, unified photo panel, tags, album trash and counters

- backend: deleting an album moves its photos to the trash without losing files (photos.album_id nullable, FK ON DELETE SET NULL, migration 000006; dropped S3 prefix delete); restore accepts an album target (album_required when the album is gone); user-scoped tags (000007) with GET /tags, POST/DELETE /photos/:id/tags, tags included in photo responses; GET /trash/count
- frontend: right-click context menus for photos (grid + viewer) and albums (rail + overview); single shared PhotoPanel reused in viewer and gallery selection (not a copy); viewer download/delete moved to the panel 'Действия'; transparent compact viewer top bar; trash entry as last rail item with per-album photo counts and trash count; album rename/delete dialogs
- openspec: sync lightroom-workspace-ui artifacts (specs photos/ui-workspace, design #24-30, tasks 9.17-9.24)

backend/internal/albums/store.go

@@ -107,3 +107,11 @@ func (s *Store) Delete(ctx context.Context, id string) error {
 	}
 	return nil
 }
+
+// TrashPhotosByAlbum soft-deletes all photos of an album so they can be restored
+// or permanently removed from the trash after the album is gone.
+func (s *Store) TrashPhotosByAlbum(ctx context.Context, albumID string) error {
+	_, err := s.pool.Exec(ctx,
+		`UPDATE photos SET deleted_at = now() WHERE album_id = $1 AND deleted_at IS NULL`, albumID)
+	return err
+}