Add Vercel Web Analytics script tag

Single line addition — Vercel serves the analytics script
at /_vercel/insights/script.js on all deployments. Tracks
page views, visitors, and referrers on the free tier.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: irparent

website/index.html

@@ -459,5 +459,6 @@ <h2 class="section-title">Team dashboards. Alerting.<br>Managed infrastructure.<
   </footer>
 
   <script src="main.js"></script>
+  <script defer src="/_vercel/insights/script.js"></script>
 </body>
 </html>