feat: Go backend, enhanced search, new widgets, Docker deploy

Major changes:
- Add Go backend (backend/) with microservices architecture
- Enhanced master-agents-svc: reranker, content-classifier, stealth-crawler,
  proxy-manager, media-search, fastClassifier, language detection
- New web-svc widgets: KnowledgeCard, ProductCard, ProfileCard, VideoCard,
  UnifiedCard, CardGallery, InlineImageGallery, SourcesPanel, RelatedQuestions
- Improved discover-svc with discover-db integration
- Docker deployment improvements (Caddyfile, vendor.sh, BUILD.md)
- Library-svc: project_id schema migration
- Remove deprecated finance-svc and travel-svc
- Localization improvements across services

Made-with: Cursor

backend/webui/next.config.mjs

@@ -0,0 +1,18 @@
+/** @type {import('next').NextConfig} */
+const nextConfig = {
+  output: 'standalone',
+  reactStrictMode: true,
+  env: {
+    API_URL: process.env.API_URL || 'http://api-gateway:3015',
+  },
+  async rewrites() {
+    return [
+      {
+        source: '/api/:path*',
+        destination: `${process.env.API_URL || 'http://api-gateway:3015'}/api/:path*`,
+      },
+    ];
+  },
+};
+
+export default nextConfig;