test(frontend): task dialog, sharing avatars, trash, API key scopes, passwords (FLAW-19)

Covers opening and closing the task dialog (the former hook-order bug),
date/time fields and the view-only mode for viewer lists, the avatar
stack of shared items, the two-tap delete in the trash, scope selection
and badges of API keys, and the shared password rule.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/__tests__/AvatarStack.test.tsx

@@ -0,0 +1,22 @@
+import { describe, it, expect } from 'vitest';
+import { render } from '@testing-library/react';
+import { AvatarStack } from '../AvatarStack';
+
+const people = ['Anna', 'Ben', 'Carla', 'Dana', 'Emil'].map((name, i) => ({ id: `u${i}`, name }));
+
+describe('AvatarStack (who a list or note is shared with)', () => {
+  it('shows at most three people and the rest as +n', () => {
+    const { container } = render(<AvatarStack people={people} />);
+    expect(container.textContent).toContain('+2');
+    expect(container.firstElementChild?.children.length).toBe(4); // 3 avatars + overflow circle
+  });
+
+  it('renders nothing for an unshared item', () => {
+    expect(render(<AvatarStack people={[]} />).container.firstChild).toBeNull();
+  });
+
+  it('needs no overflow circle when everyone fits', () => {
+    const { container } = render(<AvatarStack people={people.slice(0, 2)} />);
+    expect(container.textContent).not.toContain('+');
+  });
+});