[Bug] Refactor ```auth.py ``` to use SQLAlchemy ORM and fix Circular Imports.

Currently, the application mixes two different methods of database access:

```app.py``` uses **Flask-SQLAlchemy.**

```auth.py``` uses raw sqlite3 connections.

Problems this causes:

Database Locking: Mixing raw connections with ORM sessions on SQLite can lead to "database is locked" errors and potential corruption.

Maintenance: We are defining the User schema in multiple places (SQL definitions in auth.py vs Model definitions in app.py).

Security: Raw SQL queries are more prone to errors than ORM queries.

@abhirajadhikary06

well I already have solution for this problem , would love to initiate.