fix: upgrade CLI to new backend API and WebSocket protocol

[mooncitizen]

Summary

The backend API/WebSocket protocol changed, breaking the CLI. This commit updates the CLI to work with the new spec.

WebSocket subscription model:

• Replace subscribe_server_room/unsubscribe_server_room with subscribe_servers (per-server array subscription)
• TUI now subscribes to all user servers on WS connect
• Remove per-room unsubscribe (no longer in spec)

New WebSocket message types (server → client):

• FriendRequestDeclined, FriendRequestWithdrawn, FriendRemoved
• VoiceRoomUserSpeaking, ServerRoomCreated, ServerRoomDeleted
• UserStatusChanged, ServerMemberStatuses, ServerInviteReceived
• ServerSnapshot, RoomMessageEdited, RoomMessageDeleted, RoomTyping
• DmMessageEdited, DmMessageDeleted, UnreadCounts, UserGameActivity

New WebSocket message types (client → server):

• SetGameActivity, MarkRoomRead, MarkDmRead

REST API response format change:

• Message endpoints now return {"messages": [...], "hasMore", "nextCursor"} instead of a bare array
• Add extract_messages() helper to handle both formats
• Update all 6 call sites (chat.rs, dms.rs, join.rs, tui/app.rs)

TUI message handlers:

• Friend decline/withdraw/remove trigger friend list reload
• RoomMessageEdited/DmMessageEdited update message content in place
• RoomMessageDeleted/DmMessageDeleted remove message from list
• ServerRoomCreated/Deleted trigger server detail refresh
• UnreadCounts populates dm_unread from payload
• Remaining new types log at debug level (no-op for now)

Bug fixes:

• Fix Ctrl+C/Esc not exiting chat open (return value was discarded)
• Unwrap nested "message" field in RoomMessage WS events
• Add raw WS logging to non-persistent connections for debugging

Other:

• Add --region flag to join command for voice server region selection
• Add unit tests for all new WS message types and serialization
• Clean clippy warnings

Changes

How to test

1. Build locally and authenticate
2. Send a message directly or via the ui

Checklist

• Code compiles without warnings (cargo build --workspace)
• Tests pass (cargo test --workspace)
• I have tested this on my platform (macOS / Linux)