fix(deps): update react monorepo to v19.2.3

frontend/src/App.tsx

@@ -30,16 +30,10 @@ function App() {
   const setTheme = (theme: string) => {
     _setTheme(theme);
     localStorage.setItem("theme", theme);
-    bc.postMessage(theme);
   };
   const [toasts, setToasts] = useState<ToastMessage[]>([]);
   const [isLoading, setIsLoading] = useState(false);
 
-  const bc = new BroadcastChannel("theme-channel");
-  bc.onmessage = (ev) => {
-    _setTheme(ev.data as string);
-  };
-
   useEffect(() => {
     if (theme !== "default" && theme !== "sakura") {
       document.body.classList.remove("sakura-theme");