Add a persistent "announced" checkbox after each track's Announce button.
The state is stored in a new `announced` column on `show_tracks` and is
auto-set when the Announce button is pressed. The checkbox is also freely
togglable, and announced tracks have their Announce button disabled.
Also fixes .env leakage in test_config.py (pass _env_file=None) and adds
tests for the new DB method, API endpoint, and announce side-effect.
Made-with: Cursor
