- Add opt-out checkbox on league creation ("I want to play in this league")
so the creator can be commissioner-only without claiming a team
- Add Commissioner Management card to league settings with add/remove
commissioner UI; guards against removing the last commissioner
- Add countCommissionersByLeagueId model helper for the last-commissioner guard
- Show "No team" indicator on the league homepage next to commissioners
who don't own a team in the current season
https://claude.ai/code/session_01NSRMSYtb7jSFbngDS8okn3
