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/components/layout/Footer.tsx

@@ -8,9 +8,9 @@ const Footer = async () => {
   const currentYear = new Date().getFullYear();
 
   return (
-    <footer className="relative bg-zinc-800/50 backdrop-blur-sm border-t border-zinc-700/30 pt-8 pb-4 px-4">
+    <footer className="relative bg-zinc-800/50 backdrop-blur-sm border-t border-zinc-700/30 pt-6 sm:pt-8 pb-4 px-4 sm:px-6 lg:px-8">
       <div className="max-w-7xl mx-auto">
-        <div className="flex flex-col md:grid md:grid-cols-2 lg:grid-cols-4 gap-8">
+        <div className="flex flex-col sm:grid sm:grid-cols-2 lg:grid-cols-4 gap-6 sm:gap-8">
           {/* Contact Section */}
           <div>
             <h3 className="text-white text-base font-semibold mb-3">
@@ -92,7 +92,7 @@ const Footer = async () => {
           </div>
 
           {/* Legal Section */}
-          <div className="border-t border-zinc-700/30 pt-4">
+          <div className="border-t sm:border-t-0 lg:border-t border-zinc-700/30 pt-4 sm:pt-0 lg:pt-4">
             <div className="flex flex-col space-y-4">
               <p className="text-zinc-400 text-xs text-left">
                 &copy; {currentYear} Damjan Savić. {t('legal.copyright')}