refactor(backend): solve copilot comments

backend/app/services/.keep

@@ -1,2 +0,0 @@
-# Business logika
-

backend/app/services/user_service.py

@@ -11,9 +11,9 @@ from fastapi_users.authentication import (
 )
 from fastapi_users.db import SQLAlchemyUserDatabase
 
-from ..models.user import User
-from ..services.db import get_user_db
-from ..core.queue import enqueue_email
+from app.models.user import User
+from app.services.db import get_user_db
+from app.core.queue import enqueue_email
 
 SECRET = os.getenv("SECRET", "CHANGE_ME_SECRET")
 FRONTEND_URL = os.getenv("FRONTEND_URL", "http://localhost:5173")