feat: downgrade tech stack to stable versions and integrate GA4 error monitoring

- Downgrade Next.js 16→14.2, React 19→18.3, Tailwind 4→3.4
- Add comprehensive GA4 error monitoring system
- Create Jenkins CI/CD pipeline with quality gates
- Fix build issues: ESLint, SWC conflict, config format
- Add documentation for deployment and error tracking

next.config.mjs

@@ -0,0 +1,21 @@
+const cdnDomain = process.env.CDN_DOMAIN || '';
+
+const nextConfig = {
+  distDir: 'dist',
+  output: 'export',
+  assetPrefix: cdnDomain || undefined,
+  images: {
+    unoptimized: true,
+  },
+  compress: true,
+  poweredByHeader: false,
+  reactStrictMode: true,
+  experimental: {
+    optimizePackageImports: ['lucide-react'],
+  },
+  compiler: {
+    removeConsole: process.env.NODE_ENV === 'production',
+  },
+};
+
+export default nextConfig;