Refactor AdminPage and remove AdminPanel component: Simplify admin navigation by redirecting to preferences page and eliminating the AdminPanel component, streamlining the admin interface.

app/admin/challenges/page.tsx

@@ -0,0 +1,26 @@
+import ChallengeManagement from "@/components/admin/ChallengeManagement";
+import { Card } from "@/components/ui";
+import { challengeService } from "@/services/challenges/challenge.service";
+
+export const dynamic = "force-dynamic";
+
+export default async function AdminChallengesPage() {
+  const challenges = await challengeService.getAllChallenges();
+
+  // Sérialiser les dates pour le client
+  const serializedChallenges = challenges.map((challenge) => ({
+    ...challenge,
+    createdAt: challenge.createdAt.toISOString(),
+    acceptedAt: challenge.acceptedAt?.toISOString() ?? null,
+    completedAt: challenge.completedAt?.toISOString() ?? null,
+  }));
+
+  return (
+    <Card variant="dark" className="p-6">
+      <h2 className="text-2xl font-gaming font-bold mb-6 text-pixel-gold">
+        Gestion des Défis
+      </h2>
+      <ChallengeManagement initialChallenges={serializedChallenges} />
+    </Card>
+  );
+}