feat: add admin role management with user authentication checks and update sidebar for admin access

src/app/admin/page.tsx

@@ -0,0 +1,24 @@
+import { AdminService } from "@/lib/services/admin.service";
+import { redirect } from "next/navigation";
+import { isAdmin } from "@/lib/auth-utils";
+import { AdminContent } from "@/components/admin/AdminContent";
+
+export default async function AdminPage() {
+  try {
+    const hasAdminAccess = await isAdmin();
+    
+    if (!hasAdminAccess) {
+      redirect("/");
+    }
+
+    const [users, stats] = await Promise.all([
+      AdminService.getAllUsers(),
+      AdminService.getUserStats(),
+    ]);
+
+    return <AdminContent initialUsers={users} initialStats={stats} />;
+  } catch (error) {
+    console.error("Erreur lors du chargement de la page admin:", error);
+    redirect("/");
+  }
+}