integration: add Playwright, axe and Lighthouse CI gates

Lock SEO, accessibility and crawlability with headless browser checks so regressions fail before a merge instead of after publication.

Co-authored-by: Cursor <cursoragent@cursor.com>

e2e/contact.e2e.ts

@@ -0,0 +1,33 @@
+import { expect, test } from '@playwright/test';
+import { SITE_CONTENT_DATA } from '../src/app/core/content/site-content';
+import { SITE_CONFIG } from '../src/app/core/content/site-config';
+import { pagePath } from './helpers';
+
+test.describe('contact briefing', () => {
+  test('builds a mailto href and issues no network request', async ({ page }) => {
+    const extras: string[] = [];
+    await page.route('**/*', (route) => {
+      const url = route.request().url();
+      const resource = route.request().resourceType();
+      if (resource !== 'document' && !url.startsWith('data:') && !url.startsWith('blob:')) {
+        extras.push(`${resource} ${url}`);
+      }
+      void route.continue();
+    });
+
+    await page.goto(pagePath('contact', 'de'), { waitUntil: 'networkidle' });
+    extras.length = 0;
+
+    await page.locator('#contact-name').fill('Ada');
+    await page.locator('#contact-email').fill('ada@example.com');
+    await page.locator('#contact-projectType').selectOption('software');
+    await page.locator('#contact-situation').fill('Need a migration.');
+
+    const href = await page.locator('a.submit').getAttribute('href');
+    expect(href).toMatch(/^mailto:/);
+    expect(href).toContain(encodeURIComponent(SITE_CONTENT_DATA.de.contact.mailSubject));
+    expect(href).toContain(encodeURIComponent('Ada'));
+    expect(href).toContain(SITE_CONFIG.contactEmail);
+    expect(extras, extras.join('\n')).toEqual([]);
+  });
+});