feat: SuperAdmin bootstrap, i18n sync fix and AssetAssignment ORM fix

- Fixed AttributeError in User model (added region_code, preferred_language)
- Fixed InvalidRequestError in AssetAssignment (added organization relationship)
- Configured STATIC_DIR for translation sync
- Applied Alembic migrations for user schema updates

backend/app/db/base.py

@@ -15,6 +15,8 @@ from app.models.gamification import (  # noqa
 from app.models.system_config import SystemParameter  # noqa
 from app.models.history import AuditLog, VehicleOwnership  # noqa
 from app.models.document import Document  # noqa
+from app.models.translation import Translation  # noqa  <--- HOZZÁADVA
 from app.models.core_logic import (  # noqa
     SubscriptionTier, OrganizationSubscription, CreditTransaction, ServiceSpecialty 
-)
+)
+from app.models.security import PendingAction  # noqa  <--- CSAK A BIZTONSÁG KEDVÉÉRT, HA EZ IS HIÁNYZOTT VOLNA