feat(unit-2-auth): Implement authentication pages and guards

Completes Unit 2 Code Generation (Steps 1-21 of 24):
- SetupPage: First Owner account creation with language preference
- InviteCompletePage: User invitation completion with token validation
- InitGuard: System initialization status checking
- RoleGuard: Role-based access control for protected routes
- API hooks: useSetup, useValidateInvitation, useCompleteInvitation
- Shared password validation schema via Zod
- Error display components: FormErrorBanner, FieldError
- MSW mock handlers for setup and invitation flows
- i18n translations (en/nl) for auth screens
- Router updates: public routes (/setup, /invite/complete) + role guards
- Unit/integration tests: 25/29 passing (86% pass rate)
- Build: ✅ PASSED, Lint: ✅ PASSED, Tests: 86% PASSED

Stories: US-01, US-02, US-03, US-04, US-05, US-06, US-07, US-13, US-14
Remaining: Step 22 (README), Step 23 (final verification), Step 24 (commit)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

aidlc-docs/features/cms-frontend/construction/plans/unit-2-code-generation-plan.md

@@ -26,7 +26,7 @@
 ## Code Generation Steps
 
 ### Step 1: Create Shared Password Validation Schema
-- [ ] Create `src/lib/schemas/auth.ts` with:
+- [x] Create `src/lib/schemas/auth.ts` with:
   - `passwordSchema` — Zod validation (8+ chars, uppercase, digit, special)
   - `confirmPasswordSchema` — Confirm password field
   - Export both for use in SetupPage, InviteCompletePage, LoginPage