feat: add MFA/TOTP auth, PII encryption, agents/leads/inquiries modules, and comprehensive tests

- Add TOTP-based MFA with setup, verify, disable, backup codes, and challenge flow
- Add PII field encryption middleware with AES-256-GCM and deterministic search hashes
- Add agents, inquiries, and leads domain modules with entities, events, value objects
- Add web dashboard pages for inquiries and leads with detail dialogs
- Add 30+ component tests (valuation, charts, listings, search, providers, UI)
- Add Prisma migrations for encryption hash columns and MFA TOTP support
- Fix all ESLint errors (unused imports, duplicate imports, lint auto-fixes)
- Update dependencies and lock file
- Clean up obsolete exploration/QA docs, add audit documentation

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/components/ui/__tests__/language-switcher.spec.tsx

@@ -0,0 +1,66 @@
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { describe, expect, it, vi } from 'vitest';
+import { LanguageSwitcher } from '../language-switcher';
+
+// Mock next-intl
+vi.mock('next-intl', () => ({
+  useLocale: () => 'vi',
+  useTranslations: () => (key: string) => {
+    const translations: Record<string, string> = {
+      label: 'Ngôn ngữ',
+      vi: 'Tiếng Việt',
+      en: 'English',
+    };
+    return translations[key] ?? key;
+  },
+}));
+
+// Mock i18n navigation
+const mockReplace = vi.fn();
+vi.mock('@/i18n/navigation', () => ({
+  useRouter: () => ({
+    replace: mockReplace,
+  }),
+  usePathname: () => '/search',
+}));
+
+describe('LanguageSwitcher', () => {
+  beforeEach(() => {
+    mockReplace.mockClear();
+  });
+
+  it('renders a button', () => {
+    render(<LanguageSwitcher />);
+    expect(screen.getByRole('button')).toBeInTheDocument();
+  });
+
+  it('has correct aria-label', () => {
+    render(<LanguageSwitcher />);
+    expect(screen.getByRole('button')).toHaveAttribute(
+      'aria-label',
+      expect.stringContaining('Ngôn ngữ'),
+    );
+  });
+
+  it('shows next locale label (EN when current is VI)', () => {
+    render(<LanguageSwitcher />);
+    // The button should display the label for "en" since current is "vi"
+    expect(screen.getByText(/EN/)).toBeInTheDocument();
+  });
+
+  it('calls router.replace when clicked', async () => {
+    const user = userEvent.setup();
+    render(<LanguageSwitcher />);
+
+    await user.click(screen.getByRole('button'));
+    expect(mockReplace).toHaveBeenCalledWith('/search', { locale: 'en' });
+  });
+
+  it('has screen reader text', () => {
+    render(<LanguageSwitcher />);
+    const srText = document.querySelector('.sr-only');
+    expect(srText).toBeInTheDocument();
+    expect(srText).toHaveTextContent('English');
+  });
+});