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>

src/i18n/config.ts

@@ -59,26 +59,41 @@ export const seoKeywords: Record<Locale, string[]> = {
   de: [
     'Fullstack Developer',
     'KI Entwickler',
+    'Künstliche Intelligenz',
+    'Claude AI Entwickler',
+    'Next.js Entwickler',
+    'React Entwickler',
+    'TypeScript Entwickler',
+    'Tailwind CSS',
     'AI Agentenentwicklung',
+    'KI-Agenten Entwicklung',
     'Prozessautomatisierung',
     'Voice AI',
     'n8n Automatisierung',
+    'Python Entwickler',
     'Köln',
     'Deutschland',
   ],
   en: [
     'Fullstack Developer',
     'AI Developer',
+    'Claude AI Developer',
+    'Claude AI Integration',
+    'Next.js Developer',
+    'React Developer',
+    'TypeScript Developer',
+    'Tailwind CSS Developer',
+    'Artificial Intelligence',
+    'AI Agent Developer',
     'AI Agent Development',
     'Process Automation Expert',
     'Voice AI Developer',
     'n8n Automation',
+    'Python Developer',
+    'SaaS Development',
     'Remote Developer Europe',
     'Remote Developer USA',
     'Remote Developer UK',
-    'Python Developer',
-    'React Developer',
-    'SaaS Development',
     'Freelance AI Developer',
     'London',
     'New York',
@@ -90,10 +105,17 @@ export const seoKeywords: Record<Locale, string[]> = {
     'Fullstack Programer',
     'AI Programer Srbija',
     'AI Developer Beograd',
+    'Claude AI Developer',
+    'Next.js Programer',
+    'React Programer',
+    'TypeScript Programer',
+    'Veštačka Inteligencija',
     'Razvoj AI Agenata',
     'Automatizacija Procesa',
     'Voice AI Srbija',
     'n8n Automatizacija',
+    'Python Programer Srbija',
+    'React Programer Beograd',
     'Beograd',
     'Novi Sad',
     'Niš',
@@ -101,8 +123,6 @@ export const seoKeywords: Record<Locale, string[]> = {
     'Subotica',
     'Srbija',
     'Softverski Razvoj Srbija',
-    'Python Programer Srbija',
-    'React Programer Beograd',
     'Remote Developer Dijaspora',
     'Freelance Programer Srbija',
   ],