fix(admin-lehrer): force unique build ID to bust browser caches

Next.js was producing the same chunk hash across builds, causing
browsers to serve stale cached JS even after redeployment.

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

admin-lehrer/next.config.js

@@ -2,6 +2,8 @@
 const nextConfig = {
   output: 'standalone',
   reactStrictMode: true,
+  // Force unique build ID to bust browser caches on each deploy
+  generateBuildId: () => `build-${Date.now()}`,
   // TODO: Remove after fixing type incompatibilities from restore
   typescript: {
     ignoreBuildErrors: true,