Add host moderation controls for rooms

Hosts need practical controls to keep rooms moving and manageable.

Feedback source:
- Kicking users from rooms should be added.
- As host I wish to be able to kick/skip people whenever they are taking too long.
- Limit the amount of people who can join.

Acceptance ideas:
- Host can kick a user from a room.
- Host can force-skip or mark a user as skipping.
- Host can configure a max participant count.
- Kicked/skipped users receive a clear client message.
- Consider separate behavior for spectators vs competitors.

No files, tests, or entry points are named. Start by locating the room state and host-permission handling on the server, then trace the client path for room participant messages; done means host kick, force-skip, and participant limits work, affected users receive clear messages, and spectator behavior is defined.

Scritto dal modello di indicizzazione a partire dal testo della issue.