fix: Add root page.tsx to fix 404 on /

- Create app/page.tsx that redirects to /login
- Fixes 404 error when accessing root URL

frontend/src/app/page.tsx

@@ -0,0 +1,14 @@
+'use client';
+
+import { useEffect } from 'react';
+import { useRouter } from 'next/navigation';
+
+export default function HomePage() {
+  const router = useRouter();
+
+  useEffect(() => {
+    router.push('/login');
+  }, [router]);
+
+  return null;
+}