content: rename Kabelleitungstiefbau to Kabelleitungsnetzbau

Applied globally across MDX content, translations, and UI components including English analog terms (Cable Trenching -> Cable Network Construction).

components/layout/Footer.tsx

@@ -46,7 +46,7 @@ export function Footer({ companyInfo }: FooterProps) {
             <p className="text-neutral-400 text-base leading-relaxed max-w-sm">
               {locale === 'de'
                 ? 'Die Experten für Kabelnetzbau, Horizontalspülbohrungen und umfassende Infrastrukturprojekte. Qualität und Zuverlässigkeit aus Guben.'
-                : 'Experts in cable construction, horizontal directional drilling, and comprehensive infrastructure projects. Quality and reliability from Guben.'}
+                : 'Experts in cable network construction, horizontal directional drilling, and comprehensive infrastructure projects. Quality and reliability from Guben.'}
             </p>
           </div>