Add settings layout and page structure for authenticated routes

Introduce tabbed navigation for the settings page, including Profile, Password, Sessions, and Preferences sections. Add placeholders for each section with metadata and routes. Redirect `/settings` to `/settings/profile`. Integrate `AuthGuard` for settings and authenticated layouts while incorporating reusable `Header` and `Footer` components.

frontend/src/app/(authenticated)/settings/page.tsx

@@ -0,0 +1,10 @@
+/**
+ * Settings Index Page
+ * Redirects to /settings/profile
+ */
+
+import { redirect } from 'next/navigation';
+
+export default function SettingsPage() {
+  redirect('/settings/profile');
+}