content: rename Kabelleitungstiefbau to Kabelleitungsnetzbau

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

tests/navigation.e2e.test.ts

@@ -74,7 +74,7 @@ describe('E2E Navigation & Content (MDX Architecture)', () => {
     it('should verify blog listing and post loading', async () => {
         await page.goto(`${BASE_URL}/de/blog`, { waitUntil: 'networkidle2', timeout: 60000 });
         let bodyText = await page.evaluate(() => document.body.innerText);
-        expect(bodyText).toContain('Moderne Verfahren im Kabeltiefbau');
+        expect(bodyText).toContain('Moderne Verfahren im Kabelnetzbau');
 
         // Click on the first article (if found) or navigate directly
         await page.goto(`${BASE_URL}/de/blog/moderne-verfahren-kabeltiefbau`, { waitUntil: 'networkidle2', timeout: 60000 });