feat(12-05): create offer editor route server component

- Add src/app/admin/offers/[id]/edit/page.tsx as async server component
- Fetches getOfferEditorData(id) + getOfferFieldOptions() via Promise.all
- Calls notFound() when offer id does not exist
- Delegates rendering to OfferEditorClient

src/app/admin/offers/[id]/edit/page.tsx

@@ -0,0 +1,23 @@
+import { notFound } from "next/navigation";
+import { getOfferEditorData, getOfferFieldOptions } from "@/lib/offer-queries";
+import { OfferEditorClient } from "@/components/admin/offers/OfferEditorClient";
+
+export const revalidate = 0;
+
+export default async function OfferEditPage({
+  params,
+}: {
+  params: Promise<{ id: string }>;
+}) {
+  const { id } = await params;
+  const [data, options] = await Promise.all([
+    getOfferEditorData(id),
+    getOfferFieldOptions(),
+  ]);
+
+  if (!data) {
+    notFound();
+  }
+
+  return <OfferEditorClient data={data} fieldOptions={options} />;
+}