Fix database migration error by re-exporting Base

- Add Base import to models/base.py to re-export it properly
- Fix issue where models/__init__.py was trying to import Base from models/base.py
- Add noqa comment to suppress unused import warning
- Maintain the same model architecture but with correct imports

app/models/base.py

@@ -2,6 +2,7 @@ from sqlalchemy import Column, DateTime
 from sqlalchemy.ext.declarative import declared_attr
 from datetime import datetime
 
+from app.db.session import Base  # Re-export Base # noqa: F401
 
 
 class TimestampMixin: