fix: prevent Cloudflare from caching envs.js

envs.js is generated at container startup from environment variables.
Add Cache-Control: no-store header to ensure CDN/browser never serves
a stale version when config changes.

nextjs/headers.js

@@ -1,5 +1,15 @@
 async function headers() {
   return [
+    {
+      // envs.js is generated at container startup — must never be cached
+      source: '/assets/envs.js',
+      headers: [
+        {
+          key: 'Cache-Control',
+          value: 'no-store, no-cache, must-revalidate',
+        },
+      ],
+    },
     {
       source: '/:path*',
       headers: [