Simplify Vercel configuration and add basic test endpoint

🔧 Configuration Changes:
- Remove specific runtime version from vercel.json
- Remove buildCommand that might be causing conflicts
- Let Vercel use default Node.js runtime settings

🧪 Simple Test Endpoint:
- Add /api/simple with minimal dependencies
- Use traditional Vercel function signature (req, res)
- No imports or complex operations to isolate the issue

This should help identify if the problem is with our function configuration, imports, or Vercel setup.

api/simple.ts

@@ -0,0 +1,6 @@
+export default function handler(req: any, res: any) {
+  res.status(200).json({
+    message: 'Simple endpoint works!',
+    timestamp: new Date().toISOString()
+  });
+} 

vercel.json

@@ -45,11 +45,5 @@
         }
       ]
     }
-  ],
+  ]
-  "functions": {
-    "api/**/*.ts": {
-      "runtime": "@vercel/node@3.2.0"
-    }
-  },
-  "buildCommand": "npm run build"
 }