feat: complete MDX migration, stabilize routing and lead capture

Former-commit-id: ab5cc38c97e5f73d6e821465b90d199fb6e6edc9

tests/navigation.e2e.test.ts

@@ -86,4 +86,23 @@ describe('E2E Navigation & Content (MDX Architecture)', () => {
         const response = await page.goto(`${BASE_URL}/de/irgendwas-falsches`, { waitUntil: 'networkidle2' });
         expect(response?.status()).toBe(404);
     });
+
+    it('should verify contact form submission', async () => {
+        await page.goto(`${BASE_URL}/de/kontakt`, { waitUntil: 'load', timeout: 120000 });
+        
+        // Fill out the form
+        await page.type('input[name="name"]', 'Test User');
+        await page.type('input[name="email"]', 'testing@mintel.me');
+        await page.type('textarea[name="message"]', 'This is a test message from E2E suite.');
+        
+        // Submit the form
+        await page.click('button[type="submit"]');
+        
+        // Wait for success indicator (using content as proxy for success state)
+        await page.waitForNetworkIdle();
+        const bodyText = await page.evaluate(() => document.body.innerText);
+        
+        // The form should show a success message
+        expect(bodyText).toContain('Vielen Dank!');
+    }, 120000);
 });