- Fix ReactionGroup.count: i64 -> i32 and users: Vec<Uuid> -> Vec<String>
to match frontend ReactionItem (count: number, users: string[]).
Mismatched types caused the WS reaction update to silently fail.
Also update ReactionItem in api/ws_types.rs to match.
- Add activeRoomIdRef guard in onRoomReactionUpdated to prevent stale
room state from processing outdated events after room switch.
- Switch from prev.map() to targeted findIndex+spread in onRoomReactionUpdated
to avoid unnecessary array recreation.
