docs(unit-3): Functional design for Layout & Navigation

- Role-filtered sidebar (Owner/Admin/User visibility rules BR-U3-01–06)
- Topbar removed; UserMenu + LanguageSwitcher move to sidebar footer
- Mobile slide-over sidebar with hamburger button
- Theme toggle (light/dark) with localStorage persistence and no-flash init
- New components: MobileBar, SidebarOverlay, ThemeToggle, useTheme
- Unit 2 marked complete in aidlc-state

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

aidlc-docs/features/cms-frontend/aidlc-state.md

@@ -5,7 +5,7 @@
 - **Feature Slug**: cms-frontend
 - **Project Type**: Brownfield
 - **Start Date**: 2026-06-16T20:27:00Z
-- **Current Stage**: CONSTRUCTION - Unit 2: Code Generation — Part 2 Complete (awaiting README + verification)
+- **Current Stage**: CONSTRUCTION - Unit 3: Functional Design
 - **Branch**: unknown
 
 ## Workspace State
@@ -48,7 +48,7 @@
 ### 🟢 CONSTRUCTION PHASE (per unit)
 - [x] Unit 0 — Backend Prerequisites (CORS + httpOnly cookie) — COMPLETED 2026-06-19T11:45:00Z
 - [x] Unit 1 — Project Scaffold & Infrastructure — COMPLETED 2026-06-20T17:30:00Z
-- [x] Unit 2 — Authentication Pages — Code Generation complete 2026-06-22 (86% tests pass, build ✅)
+- [x] Unit 2 — Authentication Pages — COMPLETED 2026-06-22 (29/29 tests pass, build ✅, runtime bugs fixed)
 - [ ] Unit 3 — Layout & Navigation
 - [ ] Unit 4 — Dashboard
 - [ ] Unit 5 — User Management