feat: optimize performance and SEO, integrate Lighthouse CI

- Integrated imgproxy for centralized image optimization
- Implemented Lighthouse CI in Gitea pipeline with native Chromium
- Reached 100/100 SEO score by fixing canonicals, hreflang, and link text
- Optimized LCP by forcing Hero component visibility until hydration
- Decoupled analytics into an async shell to reduce TTI

app/[locale]/page.tsx

@@ -79,7 +79,9 @@ export async function generateMetadata({
   }
 
   const title = t('title') || 'KLZ Cables';
-  const description = t('description') || '';
+  const description =
+    t('description') ||
+    'Ihr Experte für hochwertige Stromkabel, Mittelspannungslösungen und Solarkabel. Zuverlässige Infrastruktur für eine grüne Energiezukunft.';
 
   return {
     title,