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>

frontend/vite.config.ts

@@ -0,0 +1,19 @@
+import { defineConfig } from "vite";
+import react from "@vitejs/plugin-react";
+
+export default defineConfig({
+  plugins: [react()],
+  server: {
+    port: 5173,
+    proxy: {
+      "/api": {
+        target: "http://127.0.0.1:8787",
+        changeOrigin: true,
+      },
+    },
+  },
+  build: {
+    outDir: "dist",
+    emptyOutDir: true,
+  },
+});