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/audit.md

@@ -294,6 +294,18 @@ Total: 24 steps, estimated 600–800 LOC, 4–6 hours development time. All 9 Un
 
 ---
 
+## Unit 2 Code Generation — Part 1 Approved
+
+**Timestamp**: 2026-06-20T18:15:00Z
+
+**User Input**: "Approve Plan"
+
+**AI Response**: "Plan approved. Starting Part 2 — Code Generation. Executing 24 steps to implement SetupPage, InviteCompletePage, InitGuard, RoleGuard, API hooks, tests, and MSW handlers."
+
+**Context**: Proceeding to implementation phase. Executing steps sequentially.
+
+---
+
 ## Code Generation (Unit 2) — Plan Approved
 
 **Timestamp**: 2026-06-21T09:00:00Z