test(a11y): add /chronik to AUTHENTICATED_PAGES for axe-playwright sweep

Three free axe checks light up (light / system-dark / manual-dark) without
further code changes — they run the existing parameterized spec against
/chronik.

Part of #285.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/e2e/accessibility.spec.ts

@@ -10,6 +10,7 @@ import { test, expect } from '@playwright/test';
 const AUTHENTICATED_PAGES = [
 	{ name: 'home', path: '/' },
 	{ name: 'persons', path: '/persons' },
+	{ name: 'chronik', path: '/chronik' },
 	{ name: 'admin', path: '/admin' }
 ];