- Replaced N+1 deletion pattern with a bulk `DELETE` in session cleanup for better efficiency in `session_async`.
- Updated security utilities to use HMAC-SHA256 signatures to mitigate length extension attacks and added constant-time comparisons to prevent timing attacks.
- Improved exception hierarchy with custom error types `AuthError` and `DatabaseError` for better granularity in error handling.
- Enhanced logging with `exc_info=True` for detailed error contexts across authentication services.
- Removed unused imports and reordered imports for cleaner code structure.