refactor: Migrate to Hono framework for multi-platform support

- Replace Vercel-specific handler with Hono framework
- Add Cloudflare Workers support via wrangler.toml
- Restructure project: src/index.js, src/routes/messages.js
- Update README with Cloudflare deployment instructions
- Save framework decision to memory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vercel.json

@@ -1,12 +1,12 @@
 {
+  "buildCommand": "npm run build",
+  "devCommand": "npm run dev",
+  "installCommand": "npm install",
+  "framework": null,
   "rewrites": [
     {
-      "source": "/v1/messages",
-      "destination": "/api/v1/messages"
-    },
-    {
-      "source": "/v1/:path*",
-      "destination": "/api/v1/:path*"
+      "source": "/(.*)",
+      "destination": "/api/index"
     }
   ]
 }