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/layout.e2e.ts

@@ -0,0 +1,71 @@
+import { expect, test } from '@playwright/test';
+import { SITE_CONFIG } from '../src/app/core/content/site-config';
+import { expectNoOverflow, pagePath } from './helpers';
+
+const CHECKED = [
+  pagePath('home', 'de'),
+  pagePath('home', 'en'),
+  pagePath('projects', 'de'),
+  pagePath('projects', 'en'),
+  pagePath('servicesAi', 'de'),
+  pagePath('contact', 'de'),
+  pagePath('imprint', 'en'),
+  '/missing-route',
+];
+
+test.describe('layout and crawlability', () => {
+  test('does not overflow horizontally on checked routes', async ({ page }) => {
+    for (const path of CHECKED) {
+      await page.goto(path);
+      await expectNoOverflow(page);
+    }
+  });
+
+  test('same-origin links and crawl files respond below 400', async ({ page, request }) => {
+    const seen = new Set<string>();
+    const queue = [pagePath('home', 'de'), pagePath('home', 'en')];
+
+    while (queue.length > 0) {
+      const path = queue.shift() as string;
+      if (seen.has(path)) {
+        continue;
+      }
+      seen.add(path);
+
+      await page.goto(path);
+      const urls = await page.evaluate(() => {
+        const values = [
+          ...Array.from(document.querySelectorAll('a[href]'), (node) => node.getAttribute('href')),
+          ...Array.from(document.querySelectorAll('[src]'), (node) => node.getAttribute('src')),
+        ];
+        return values.filter(
+          (value): value is string => typeof value === 'string' && value.length > 0,
+        );
+      });
+
+      for (const raw of urls) {
+        if (raw.startsWith('mailto:') || raw.startsWith('tel:') || raw.startsWith('#')) {
+          continue;
+        }
+
+        const resolved = new URL(raw, page.url());
+        if (resolved.origin !== new URL(page.url()).origin) {
+          continue;
+        }
+
+        const next = `${resolved.pathname}${resolved.search}`;
+        const response = await request.get(next);
+        expect(response.status(), `${raw} from ${path}`).toBeLessThan(400);
+
+        if (!seen.has(next) && !next.includes('.')) {
+          queue.push(next);
+        }
+      }
+    }
+
+    for (const asset of ['/robots.txt', '/sitemap.xml', '/llms.txt', SITE_CONFIG.cvAssetPath]) {
+      const response = await request.get(asset);
+      expect(response.status(), asset).toBe(200);
+    }
+  });
+});