fix(vercel): disable HTML caching for SPA index pages

Rewrite cache was serving stale index.html with old asset hashes after
deploys. Adding must-revalidate to non-asset paths under /_studio/,
/_account/, and /_dashboard/ ensures the CDN refetches index.html on
every deploy.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: hotlong

apps/objectos/vercel.json

@@ -33,6 +33,24 @@
       "headers": [
         { "key": "Cache-Control", "value": "public, max-age=31536000, immutable" }
       ]
+    },
+    {
+      "source": "/_studio/:path((?!assets/).*)?",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=0, must-revalidate" }
+      ]
+    },
+    {
+      "source": "/_account/:path((?!assets/).*)?",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=0, must-revalidate" }
+      ]
+    },
+    {
+      "source": "/_dashboard/:path((?!assets/).*)?",
+      "headers": [
+        { "key": "Cache-Control", "value": "public, max-age=0, must-revalidate" }
+      ]
     }
   ],
   "redirects": [