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/a11y.e2e.ts

@@ -0,0 +1,48 @@
+import AxeBuilder from '@axe-core/playwright';
+import { expect, test } from '@playwright/test';
+import { pagePath } from './helpers';
+
+const AXE_PATHS = [
+  pagePath('home', 'de'),
+  pagePath('home', 'en'),
+  pagePath('projects', 'de'),
+  pagePath('projects', 'en'),
+  pagePath('servicesAi', 'de'),
+  pagePath('servicesAi', 'en'),
+  pagePath('contact', 'de'),
+  pagePath('contact', 'en'),
+  pagePath('imprint', 'de'),
+  pagePath('imprint', 'en'),
+  '/missing-route',
+  '/en/missing-route',
+];
+
+test.describe('accessibility', () => {
+  test('revealed content stays visible under reduced motion', async ({ page }) => {
+    await page.emulateMedia({ reducedMotion: 'reduce' });
+    await page.goto(pagePath('home', 'de'));
+    const pending = page.locator('.reveal-pending');
+    await expect(pending).toHaveCount(0);
+    await expect(page.locator('app-systems-map')).toBeVisible();
+    await expect(page.locator('app-case-card').first()).toBeVisible();
+  });
+
+  for (const path of AXE_PATHS) {
+    test(`axe has no serious or critical violations on ${path}`, async ({ page }) => {
+      await page.goto(path);
+      const results = await new AxeBuilder({ page }).analyze();
+      const blocking = results.violations.filter(
+        (violation) => violation.impact === 'serious' || violation.impact === 'critical',
+      );
+
+      const details = blocking
+        .map((violation) => {
+          const nodes = violation.nodes.map((node) => node.target.join(' ')).join(', ');
+          return `${violation.id} (${violation.impact}): ${nodes}`;
+        })
+        .join('\n');
+
+      expect(blocking, details).toEqual([]);
+    });
+  }
+});