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/main.tsx.bak

@@ -0,0 +1,46 @@
+// main.tsx
+import { createRoot } from 'react-dom/client';
+import { HelmetProvider } from 'react-helmet-async';
+import App from './App';
+import './index.css';
+import './styles/mobile-optimizations.css';
+import './styles/minimal-fixes.css';
+import './i18n';
+import { register as registerServiceWorker } from './utils/serviceWorkerRegistration';
+import { reportWebVitals } from './utils/webVitals';
+import { initializeFonts } from './utils/fontLoader';
+
+// Typdefinition für Google Analytics
+declare global {
+    interface Window {
+        dataLayer: unknown[];
+        gtag: (command: string, ...args: unknown[]) => void;
+        initializeAnalytics: () => void;
+    }
+}
+
+// Initialize fonts as early as possible
+initializeFonts();
+
+const rootElement = document.getElementById('root');
+
+if (!rootElement) {
+    throw new Error('Root element not found');
+}
+
+createRoot(rootElement).render(
+    <HelmetProvider>
+        <App />
+    </HelmetProvider>
+);
+
+// Mark app as mounted to prevent flicker
+requestAnimationFrame(() => {
+    document.body.classList.add('app-mounted');
+});
+
+// Register service worker
+registerServiceWorker();
+
+// Report Web Vitals
+reportWebVitals();