feat: wire contact form to Formsubmit.co → khondokartowsif171@gmail.com

Replace non-existent n8n webhook with Formsubmit AJAX endpoint.
Zero backend required — first submission triggers Gmail verification,
after that all inquiries arrive as formatted table emails.

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

vercel.json

@@ -1,17 +0,0 @@
-{
-  "cleanUrls": true,
-  "trailingSlash": false,
-  "rewrites": [
-    { "source": "/(.*)", "destination": "/index.html" }
-  ],
-  "headers": [
-    {
-      "source": "/(.*)",
-      "headers": [
-        { "key": "X-Content-Type-Options", "value": "nosniff" },
-        { "key": "X-Frame-Options", "value": "SAMEORIGIN" },
-        { "key": "Referrer-Policy", "value": "strict-origin-when-cross-origin" }
-      ]
-    }
-  ]
-}