Delete dead Flask-based PAL24 webhook server (app/external/pal24_webhook.py).
PAL24 webhooks already handled by unified FastAPI server on port 8080.
- Remove flask dependency from pyproject.toml and requirements.txt
- Remove PAL24_WEBHOOK_PORT config (unused, FastAPI uses shared port)
- Remove pal24_webhook module reference from log filter
- Update docs: webhook example rewritten from Flask to FastAPI
- Uninstall flask, werkzeug, blinker, itsdangerous
- Add pyproject.toml with uv and ruff configuration
- Pin Python version to 3.13 via .python-version
- Add Makefile commands: lint, format, fix
- Apply ruff formatting to entire codebase
- Remove unused imports (base64 in yookassa/simple_subscription)
- Update .gitignore for new config files