test(e2e): update account page heading assertion to match redesign

8612042 dropped the static "Account Management" heading in favor of the
account name (rendered as a dynamic h1). Switch the smoke test to the
"Settings" SectionLabel — a stable h2 that survives the redesign.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/e2e/navigation.spec.ts

@@ -30,7 +30,7 @@ test.describe('authenticated navigation smoke tests', () => {
     await page.goto('/account')
 
     await expect(
-      page.getByRole('heading', { name: 'Account Management' }),
+      page.getByRole('heading', { name: 'Settings' }),
     ).toBeVisible()
   })
 })