feat: add NotificationHandler component to layout

- Integrated `NotificationHandler` into the app layout for centralized notification management.
- Ensured compatibility with existing `Toaster` component for consistent user feedback.

frontend/src/app/layout.tsx

@@ -1,5 +1,6 @@
 import type { Metadata } from "next";
 import { Ubuntu_Mono, Ubuntu_Sans } from "next/font/google";
+import { NotificationHandler } from "@/components/notification-handler";
 import { Toaster } from "@/components/ui/sonner";
 import { AudioProvider } from "@/providers/audio-provider";
 import { AuthProvider } from "@/providers/auth-provider";
@@ -76,6 +77,7 @@ export default function RootLayout({
 						<SocketProvider>
 							<AudioProvider>
 								{children}
+								<NotificationHandler />
 								<Toaster />
 							</AudioProvider>
 						</SocketProvider>