🐛 fix(__main__.py): check if port is in use and get a free port if it is

✨ feat(__main__.py): add support for health check endpoint and use it to check server status
The `serve` function now checks if the specified port is in use and gets a free port if it is. This ensures that the server can run on a free port and avoids conflicts with other running applications. The `serve` function also now uses a health check endpoint to check the status of the server. The `setup_static_files` function now takes a `Path` object instead of a string for the static files directory. The `create_app` function now takes a `Path` object instead of a string for the static files directory.