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/sessions/page.tsx

@@ -0,0 +1,23 @@
+/**
+ * Session Management Page
+ * View and manage active sessions across devices
+ */
+
+import type { Metadata } from 'next';
+
+export const metadata: Metadata = {
+  title: 'Active Sessions',
+};
+
+export default function SessionsPage() {
+  return (
+    <div>
+      <h2 className="text-2xl font-semibold text-gray-900 dark:text-white mb-4">
+        Active Sessions
+      </h2>
+      <p className="text-gray-600 dark:text-gray-400">
+        Manage your active sessions (Coming in Task 3.4)
+      </p>
+    </div>
+  );
+}