feat: add admin layout with sidebar, auth guard, and navbar link

- Admin layout with server-side auth guard (redirects non-admins)
- Reusable sidebar component with active state detection
- Navbar profile dropdown shows admin link for admin users
- Admin routes are noindexed (robots: false)
- /admin redirects to /admin/users

lib/routes.ts

@@ -39,4 +39,22 @@ export const authRoutes = [
         href: "/profile?tab=saved",
         icon: "Bookmark",
     },
+]
+
+export const adminRoutes = [
+    {
+        title: "Users",
+        href: "/admin/users",
+        icon: "Users",
+    },
+    {
+        title: "Hardware",
+        href: "/admin/hardware",
+        icon: "Cpu",
+    },
+    {
+        title: "Games",
+        href: "/admin/games",
+        icon: "Gamepad2",
+    },
 ]