Enable clean URLs on Vercel so sub-pages resolve

The static build emits <route>.html files, but Vercel was not mapping
extensionless paths to them, so direct loads of /get, /ocd, /toolkit,
/blog, etc. returned 404 (they only worked via client-side navigation).
This broke the ad landing page and returned 404s to crawlers on every
sub-page. cleanUrls serves /get from get.html and redirects .html to the
clean URL; trailingSlash:false keeps canonicals consistent.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: maskedsyntax

website/vercel.json

@@ -1,4 +1,6 @@
 {
   "buildCommand": "npm run build",
-  "outputDirectory": "build"
+  "outputDirectory": "build",
+  "cleanUrls": true,
+  "trailingSlash": false
 }