fix(alerts): import User model in operational_alert_service to fix NameError in _dispatch_inapp_notifications

backend/app/services/operational_alert_service.py

@@ -20,6 +20,7 @@ from app.models.ownership_queue import RevalidationQueueItem, QueueStatus
 from app.models.ownership_queue import TechniqueOwnership
 from app.models.executive_dashboard import PostureSnapshot
 from app.models.enums import TechniqueStatus
+from app.models.user import User
 
 log = logging.getLogger(__name__)