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>

.eslintignore

@@ -0,0 +1,16 @@
+# Old Vite files
+src/components-vite/
+src/pages-vite/
+src/hooks/
+src/services/
+src/utils/
+src/i18n/locales-old/
+*.bak
+
+# Build output
+.next/
+dist/
+build/
+
+# Dependencies
+node_modules/