Adds `/new-game ranked` slash command for human-vs-human ranked games.
Sets `game_type='ranked'` and `ranked=True` on the Game model.
Also adds 'ranked' case to `get_scorebug_embed` so scorebug title
shows '- Ranked' instead of falling through to '- Unlimited'.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>