Tailwind v4 migration, massive SEO optimization, and fixes

- Migrate to Tailwind CSS v4 with @theme, @layer, @plugin syntax
- Upgrade to Next.js 16.1, React 19.2, TypeScript 5.9.3
- Add 8 technology landing pages (Next.js, React, TypeScript, Tailwind CSS, Claude AI, Python, n8n, KI-Agenten)
- Expand SEO keywords across all locales (de/en/sr) for home, layout, cities, services
- Add tech-specific keywords to all 22 city pages
- Add FAQ schema + seoKeywords to service detail pages
- Add CollectionPage JSON-LD to blog listing
- Fix city page: dynamic region, BASE_URL canonicals, x-default hreflang
- Rewrite terms page with full German AGB, English and Serbian translations
- Remove dead crypto import and unused CSRF middleware (Edge Runtime fix)
- Remove crawlDelay from robots.ts
- Update sitemap with technology pages (~198 indexed URLs)
- Remove deprecated tailwind.config.js

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -23,7 +23,7 @@
     "@mdx-js/mdx": "^3.1.0",
     "@mdx-js/react": "^3.1.0",
     "@next-safe/middleware": "^0.10.0",
-    "@next/mdx": "^15.1.0",
+    "@next/mdx": "^16.1.0",
     "@supabase/ssr": "^0.8.0",
     "@supabase/supabase-js": "^2.39.7",
     "class-variance-authority": "^0.7.1",
@@ -31,13 +31,13 @@
     "framer-motion": "^11.18.2",
     "gray-matter": "^4.0.3",
     "lucide-react": "^0.475.0",
-    "next": "^15.1.0",
-    "next-intl": "^3.26.0",
+    "next": "^16.1.0",
+    "next-intl": "^4.7.2",
     "next-mdx-remote": "^5.0.0",
     "openai": "^4.77.0",
     "pg": "^8.13.1",
-    "react": "^19.0.0",
-    "react-dom": "^19.0.0",
+    "react": "^19.2.0",
+    "react-dom": "^19.2.0",
     "react-ga4": "^2.1.0",
     "react-intersection-observer": "^9.8.1",
     "tailwind-merge": "^3.0.1",
@@ -46,24 +46,24 @@
   },
   "devDependencies": {
     "@playwright/test": "^1.58.0",
-    "@tailwindcss/forms": "^0.5.7",
+    "@tailwindcss/forms": "^0.5.11",
+    "@tailwindcss/postcss": "^4.1.0",
     "@testing-library/jest-dom": "^6.0.0",
-    "@testing-library/react": "^14.0.0",
+    "@testing-library/react": "^16.1.0",
     "@types/mdx": "^2.0.13",
     "@types/node": "^22.0.0",
     "@types/pg": "^8.11.10",
-    "@types/react": "^19.0.0",
-    "@types/react-dom": "^19.0.0",
+    "@types/react": "^19.2.0",
+    "@types/react-dom": "^19.2.0",
     "@vitest/coverage-v8": "1.6.1",
-    "autoprefixer": "^10.4.18",
     "eslint": "^9.9.1",
-    "eslint-config-next": "^15.1.0",
+    "eslint-config-next": "^16.1.0",
     "jsdom": "^23.2.0",
     "playwright-lighthouse": "^4.0.0",
     "postcss": "^8.4.35",
     "sharp": "^0.34.3",
-    "tailwindcss": "^3.4.1",
-    "typescript": "^5.5.3",
+    "tailwindcss": "^4.1.0",
+    "typescript": "5.9.3",
     "vitest": "^1.3.1"
   }
 }