Poker Planning - Add Observer Login

### Package / App

MAD Components

### Description

Implement an Observer role that allows users to join a Planning Poker session without participating in voting. Observers can watch the session in real time but cannot cast story point or confidence votes.

**Requirements**

1. Add an "Join as Observer" checkbox or toggle on the login/join screen.
2. When selected, the user joins the room with the Observer role.
3. Multiple observers should be allowed in the same room.
4. Observers should:
- Be visible in the participant list with an Observer badge or label.
- Receive all real-time room updates (users joining/leaving, votes, reveal, reset, etc.).
- Be able to view revealed votes, confidence levels, averages, and vote distribution.
- Not be able to cast story point votes.
- Not be able to cast confidence votes.
- Not be counted when determining whether all participants have voted.
- Not be included in average calculations or vote statistics.

### Alternatives

_No response_

### Other info

_No response_