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/components-vite/ResponsiveImage.tsx

@@ -0,0 +1,44 @@
+interface ResponsiveImageProps {
+  src: string;
+  alt: string;
+  className?: string;
+  sizes?: string;
+  loading?: 'lazy' | 'eager';
+  fetchpriority?: 'high' | 'low' | 'auto';
+}
+
+export default function ResponsiveImage({
+                                          src,
+                                          alt,
+                                          className = '',
+                                          sizes = '100vw',
+                                          loading = 'lazy',
+                                          fetchpriority = 'auto'
+                                        }: ResponsiveImageProps) {
+  // Generate Unsplash responsive URLs
+  const generateSrcSet = (url: string) => {
+    if (!url.includes('unsplash.com')) return undefined;
+
+    const widths = [640, 750, 828, 1080, 1200, 1920, 2048, 3840];
+    return widths
+        .map((w) => {
+          const modifiedUrl = url.replace(/w=\d+/, `w=${w}`);
+          return `${modifiedUrl} ${w}w`;
+        })
+        .join(', ');
+  };
+
+  const srcSet = generateSrcSet(src);
+
+  return (
+      <img
+          src={src}
+          alt={alt}
+          className={className}
+          loading={loading}
+          fetchpriority={fetchpriority}
+          sizes={sizes}
+          srcSet={srcSet}
+      />
+  );
+}