feat: migrate to Cloudflare Workers with icon and version upload

Replace Express/SQLite and web/ with frontend/, worker/, and wrangler deploy. Add optional app icon upload, date-based app_version, and build-app workflow input.

Co-authored-by: Cursor <cursoragent@cursor.com>

worker/src/index.ts

@@ -0,0 +1,19 @@
+import type { Env } from "./env";
+import { handleBuildsRequest } from "./routes/builds";
+import { jsonResponse } from "./lib/response";
+
+export default {
+  async fetch(request: Request, env: Env): Promise<Response> {
+    const url = new URL(request.url);
+
+    if (url.pathname === "/api/health") {
+      return jsonResponse({ ok: true });
+    }
+
+    if (url.pathname.startsWith("/api/builds")) {
+      return handleBuildsRequest(request, env, url);
+    }
+
+    return env.ASSETS.fetch(request);
+  },
+};