feat(T02): vehicle management + mobile.de push + vehicle UI

- Vehicle model: 25+ fields, 5 vehicle types, soft-delete
- Vehicle CRUD: 7 API endpoints with JWT auth, filter/sort/paginate
- mobile.de: push/update/delete listings, field mapping, retry logic
- MobileDeListing model for sync status tracking
- Frontend: VehicleList, VehicleForm, VehicleDetail, MobileDeStatus
- 73 backend tests (82% coverage), 16 frontend tests

frontend/app/[locale]/fahrzeuge/[id]/page.tsx

@@ -0,0 +1,14 @@
+import { VehicleDetail } from '@/components/vehicles/VehicleDetail';
+
+export default async function FahrzeugDetailPage({
+  params,
+}: {
+  params: Promise<{ locale: string; id: string }>;
+}) {
+  const { id } = await params;
+  return (
+    <div className="max-w-4xl mx-auto p-6">
+      <VehicleDetail vehicleId={id} />
+    </div>
+  );
+}