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
Add a "Send IRC Message" section to the admin dashboard that sends a
configurable privmsg to any IRC nick or channel via all connected bots.
New POST /admin/ping endpoint broadcasts a "privmsg" WebSocket message
type, handled by both Limnoria and Sopel plugins.
Also enable pydantic-settings .env file loading (python-dotenv) and
add .env.example documenting all NTR_* configuration variables.
Made-with: Cursor
