♻️(frontend) introduce useRoomId hook

Manipulating the room's id from the react-query cache should be
encapsulated in a dedicated hook.

src/frontend/src/features/rooms/livekit/hooks/useRoomId.ts

@@ -0,0 +1,6 @@
+import { useRoomData } from './useRoomData'
+
+export const useRoomId = () => {
+  const apiRoomData = useRoomData()
+  return apiRoomData?.livekit?.room
+}