fix part 3

backend/app/database/base.py

@@ -1,10 +1,9 @@
 """Base model for all database models."""
 
-from datetime import datetime, timezone
 from typing import Any
 from uuid import uuid4
 
-from sqlalchemy import Column, DateTime
+from sqlalchemy import Column, DateTime, func
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import DeclarativeBase, declared_attr
 
@@ -22,7 +21,7 @@ class Base(DeclarativeBase):
 
     # Common columns for all models
     id: Any = Column(UUID(as_uuid=True), primary_key=True, default=uuid4)
-    created_at: Any = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
+    created_at: Any = Column(DateTime, server_default=func.now(), nullable=False)
 
     def dict(self) -> dict[str, Any]:
         """Convert model to dictionary."""