- Fixed the `AttributeError: 'User' object has no attribute '_password'` by properly mapping the `_password` attribute to the `password` column in the database.
- Updated the `User` model to ensure passwords are only hashed once during creation and not re-hashed when retrieved or updated.
- Improved the `check_password` method to correctly compare hashed passwords.
- Verified the signup and login flow to ensure consistent behavior
