feat(frontend): add management portal landing page

frontend/site/scripts/prepare-sites-build.mjs

@@ -0,0 +1,21 @@
+#!/usr/bin/env node
+import { copyFileSync, existsSync, mkdirSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const dist = path.join(root, "dist");
+const index = path.join(dist, "client", "index.html");
+const worker = path.join(root, "worker", "index.js");
+const hosting = path.join(root, ".openai", "hosting.json");
+
+for (const file of [index, worker, hosting]) {
+  if (!existsSync(file)) throw new Error("Missing Sites build input: " + file);
+}
+
+mkdirSync(path.join(dist, "server"), { recursive: true });
+mkdirSync(path.join(dist, ".openai"), { recursive: true });
+copyFileSync(worker, path.join(dist, "server", "index.js"));
+copyFileSync(hosting, path.join(dist, ".openai", "hosting.json"));
+
+console.log("Prepared Sites build: dist/server/index.js and dist/.openai/hosting.json");