- Replaced `not UserSession.is_active` with `UserSession.is_active == False` in cleanup queries for explicit comparison.
- Added `mypy` overrides for `app.alembic` and external libraries (`starlette`).
- Refactored `Makefile` to use virtual environment binaries for commands like `ruff`, `mypy`, and `pytest`.
- Introduced `pyproject.toml` to centralize backend tool configurations (e.g., Ruff, mypy, coverage, pytest).
- Replaced Black, isort, and Flake8 with Ruff for linting, formatting, and import sorting.
- Updated `requirements.txt` to include Ruff and remove replaced tools.
- Added `Makefile` to streamline development workflows with commands for linting, formatting, type-checking, testing, and cleanup.
