Improved structure and added caching for server messages

src/hooks/use-app.ts

@@ -7,8 +7,7 @@ import useUser, { UserProfile } from "./get-user";
 export default function useApp(): App {
   const node = useRef<WebSocket | null>(null);
   const [profiles, setProfiles] = useState<StringMap<UserProfile>>({});
-  const messages = useMessages((s) => s.messages);
-  const addMessage = useMessages((s) => s.addMessage);
+  const { messages, addMessage } = useMessages();
   const [sidebarOpen, setSidebarOpen] = useState(true);
   const profile = useUser();