- Deleted outdated backend test cases (`test_auth.py`, `test_rate_limiting.py`, `test_users.py`) to clean up deprecated test structure.
- These tests are now redundant with newer async test implementations and improved coverage.
- Refactored all `password reset` and `auth dependency` tests to utilize async patterns for compatibility with async database sessions.
- Enhanced test fixtures with `pytest-asyncio` to support asynchronous database operations.
- Improved user handling with async context management for `test_user` and `async_mock_user`.
- Introduced `await` syntax for route calls, token generation, and database transactions in test cases.
- Added security headers middleware to enforce best practices (e.g., XSS and clickjacking prevention, CSP, HSTS in production).
- Updated `User` model schema: refined field constraints and switched `preferences` to `JSONB` for PostgreSQL compatibility.
- Introduced tests to validate security headers across endpoints and error responses.
- Ensured headers like `X-Frame-Options`, `X-Content-Type-Options`, and `Permissions-Policy` are correctly configured.
