T07a: frontend core SPA — shell + auth + routing + i18n + UI library + a11y

- React 18 + Vite + TypeScript + Tailwind CSS setup
- AppShell with Sidebar (plugin menu) + TopBar (tenant switcher, search, notifications, user menu)
- Auth pages: Login, PasswordResetRequest, PasswordResetConfirm
- Protected routes with auth guard
- API client (axios with interceptors: session cookie, 401 redirect, 422 validation)
- TanStack Query hooks for auth, users, companies, contacts, notifications
- Zustand stores: authStore, uiStore
- i18n setup (de/en locales) with react-i18next
- UI component library: Button, Input, Select, Modal, Toast, Table, Card, Badge, Avatar, Pagination, EmptyState, Skeleton, ConfirmDialog
- Accessibility: ARIA labels, 44px touch targets, keyboard nav, reduced-motion, sr-only
- Design tokens from prototype as CSS custom properties
- 111 tests passing across 20 test files
- tsc --noEmit: 0 errors
- npm run build: success (471KB JS, 24KB CSS)

frontend/src/__tests__/ui/ConfirmDialog.test.tsx

@@ -0,0 +1,46 @@
+import React from 'react';
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen, fireEvent } from '@testing-library/react';
+import { ConfirmDialog } from '@/components/ui/ConfirmDialog';
+
+describe('ConfirmDialog', () => {
+  it('renders nothing when open=false', () => {
+    render(<ConfirmDialog open={false} message="Wirklich löschen?" onConfirm={() => {}} onCancel={() => {}} />);
+    expect(screen.queryByText('Wirklich löschen?')).not.toBeInTheDocument();
+  });
+
+  it('renders message when open=true', () => {
+    render(<ConfirmDialog open={true} message="Wirklich löschen?" onConfirm={() => {}} onCancel={() => {}} />);
+    expect(screen.getByText('Wirklich löschen?')).toBeInTheDocument();
+  });
+
+  it('calls onConfirm when confirm button clicked', () => {
+    const onConfirm = vi.fn();
+    render(<ConfirmDialog open={true} message="Löschen?" onConfirm={onConfirm} onCancel={() => {}} />);
+    fireEvent.click(screen.getByRole('button', { name: 'Bestätigen' }));
+    expect(onConfirm).toHaveBeenCalledTimes(1);
+  });
+
+  it('calls onCancel when cancel button clicked', () => {
+    const onCancel = vi.fn();
+    render(<ConfirmDialog open={true} message="Löschen?" onConfirm={() => {}} onCancel={onCancel} />);
+    fireEvent.click(screen.getByRole('button', { name: 'Abbrechen' }));
+    expect(onCancel).toHaveBeenCalledTimes(1);
+  });
+
+  it('renders default title', () => {
+    render(<ConfirmDialog open={true} message="Test" onConfirm={() => {}} onCancel={() => {}} />);
+    expect(screen.getByText('Bestätigung erforderlich')).toBeInTheDocument();
+  });
+
+  it('renders custom title', () => {
+    render(<ConfirmDialog open={true} title="Löschen bestätigen" message="Test" onConfirm={() => {}} onCancel={() => {}} />);
+    expect(screen.getByText('Löschen bestätigen')).toBeInTheDocument();
+  });
+
+  it('uses danger variant button when variant=danger', () => {
+    render(<ConfirmDialog open={true} variant="danger" message="Test" onConfirm={() => {}} onCancel={() => {}} />);
+    const confirmBtn = screen.getByRole('button', { name: 'Bestätigen' });
+    expect(confirmBtn.className).toContain('bg-danger-600');
+  });
+});