Add host moderation controls for rooms

[coder13]

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.