web: adopt Cache Components, Partial Prefetching and ensureStatic

web/src/app/preview/render/page.tsx

@@ -74,8 +74,10 @@ import {
   VenueRentalIndexFragment,
 } from "@/gql/graphql";
 import { cookies } from "next/headers";
-export const dynamic = "force-dynamic";
-export const revalidate = 0;
+
+// Rendered per request from the editor's preview cookie; there is nothing
+// to prerender, so let the route block instead of requiring a loading shell
+export const instant = false;
 
 const previewPageQuery = graphql(`
   query previewPage($token: String!) {