test(e2e): stabilize Playwright suite and close plan verification

Make auth/tasks/shifts end-to-end tests deterministic with robust role-aware
fallbacks, single-worker execution, and non-brittle selectors aligned to the
current UI contracts.

Mark verified plan/evidence checklists complete after re-validating backend,
frontend, E2E, security isolation, and infrastructure commands.

frontend/e2e/smoke.spec.ts

@@ -2,5 +2,5 @@ import { test, expect } from '@playwright/test';
 
 test('homepage loads successfully', async ({ page }) => {
   await page.goto('/');
-  await expect(page).toHaveTitle(/Next App/);
+  await expect(page).toHaveTitle(/WorkClub Manager/);
 });