Migrate from Vite to Next.js 15 with SSR

- Replace Vite + React Router with Next.js 15 App Router
- Implement i18n with next-intl (URL-based: /de, /en, /sr)
- Add SSR/SSG for all pages (48 static pages generated)
- Setup Supabase SSR client for auth
- Migrate all pages: Home, About, Portfolio, Blog, Contact, Login, Dashboard, Imprint, Privacy, Terms
- Add Docker support with standalone output
- Replace i18next with next-intl JSON translations
- Use next/image for optimized images

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

next.config.ts

@@ -0,0 +1,67 @@
+import type { NextConfig } from 'next';
+import createMDX from '@next/mdx';
+import createNextIntlPlugin from 'next-intl/plugin';
+
+const withNextIntl = createNextIntlPlugin('./src/i18n/request.ts');
+
+const nextConfig: NextConfig = {
+  output: 'standalone',
+
+  pageExtensions: ['js', 'jsx', 'md', 'mdx', 'ts', 'tsx'],
+
+  images: {
+    formats: ['image/avif', 'image/webp'],
+    deviceSizes: [640, 750, 828, 1080, 1200, 1920, 2048],
+    imageSizes: [16, 32, 48, 64, 96, 128, 256, 384],
+    remotePatterns: [
+      {
+        protocol: 'https',
+        hostname: 'mxadgucxhmstlzsbgmoz.supabase.co',
+      },
+    ],
+  },
+
+  experimental: {
+    optimizePackageImports: ['lucide-react', 'framer-motion'],
+  },
+
+  async headers() {
+    return [
+      {
+        source: '/:path*',
+        headers: [
+          {
+            key: 'X-DNS-Prefetch-Control',
+            value: 'on',
+          },
+          {
+            key: 'X-Frame-Options',
+            value: 'SAMEORIGIN',
+          },
+          {
+            key: 'X-Content-Type-Options',
+            value: 'nosniff',
+          },
+        ],
+      },
+      {
+        source: '/fonts/:path*',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 'public, max-age=31536000, immutable',
+          },
+        ],
+      },
+    ];
+  },
+};
+
+const withMDX = createMDX({
+  options: {
+    remarkPlugins: [],
+    rehypePlugins: [],
+  },
+});
+
+export default withNextIntl(withMDX(nextConfig));