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>

src/pages-vite/NotFoundPage.tsx

@@ -0,0 +1,40 @@
+import { useNavigate } from 'react-router-dom';
+import { FileQuestion } from 'lucide-react';
+import SEO from '../components/SEO';
+
+const NotFoundPage = () => {
+  const navigate = useNavigate();
+
+  return (
+    <>
+      <SEO 
+        title="404 - Page Not Found"
+        description="The page you're looking for doesn't exist."
+      />
+      <div className="min-h-screen flex items-center justify-center p-4">
+        <div className="text-center">
+          <FileQuestion className="h-16 w-16 text-orange-500 mx-auto mb-6" />
+          <h1 className="text-4xl font-bold mb-4">404</h1>
+          <p className="text-xl mb-2">Page Not Found</p>
+          <p className="text-white/70 mb-8">The page you're looking for doesn't exist or has been moved.</p>
+          <div className="space-x-4">
+            <button
+              onClick={() => navigate(-1)}
+              className="bg-gray-800 hover:bg-gray-700 text-white px-6 py-2 rounded-lg transition-colors"
+            >
+              Go Back
+            </button>
+            <button
+              onClick={() => navigate('/')}
+              className="bg-orange-500 hover:bg-orange-600 text-white px-6 py-2 rounded-lg transition-colors"
+            >
+              Home Page
+            </button>
+          </div>
+        </div>
+      </div>
+    </>
+  );
+};
+
+export default NotFoundPage