docs(unit-3): Revert to open questions in functional design plan

Functional design documents were written based on self-answered questions
instead of asking the user. Removed pre-written docs and restored the plan
with open questions for the user to answer.

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

aidlc-docs/features/cms-frontend/construction/unit-3/functional-design/business-logic-model.md

@@ -1,56 +0,0 @@
-# Business Logic Model — Unit 3: Layout & Navigation
-
-## Component Hierarchy
-
-```
-AppLayout
-├── Sidebar (desktop: always visible)
-│   ├── Logo / AppName
-│   ├── NavList (role-filtered NavItems)
-│   │   └── NavItem (Link with activeProps)
-│   └── SidebarFooter
-│       ├── LanguageSwitcher
-│       ├── ThemeToggle
-│       └── UserMenu (name, email, logout)
-├── MobileBar (mobile only — hamburger + app name)
-│   └── opens → SidebarOverlay (Sidebar rendered in overlay)
-└── <main>
-    └── <Outlet />
-```
-
-## Theme Initialisation (no flash)
-
-Theme is applied in a blocking inline script in `index.html` — before React hydrates — to prevent a flash of the wrong theme:
-
-```html
-<script>
-  (function() {
-    var stored = localStorage.getItem('cms-theme');
-    var theme = stored || (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light');
-    document.documentElement.classList.add(theme);
-  })();
-</script>
-```
-
-React's `useTheme` hook reads from `localStorage` on mount and keeps the toggle in sync.
-
-## NavItem Filtering Logic
-
-```ts
-const visibleItems = NAV_ITEMS.filter(item =>
-    !item.roles || item.roles.includes(user.role)
-);
-```
-
-`item.roles` being `undefined` means "visible to everyone". This is evaluated at render time whenever `user.role` changes.
-
-## Mobile Sidebar State
-
-Local `useState<boolean>` in `AppLayout` (or `MobileBar`). The sidebar overlay uses a `<dialog>` or a Tailwind-animated `translate-x` panel. Closes on:
-- Backdrop click (`onBackdropClick`)
-- Close button click
-- TanStack Router navigation (via `useEffect` watching `location.pathname`)
-
-## Logout Flow (unchanged from Unit 1/2)
-
-`UserMenu` in sidebar footer calls `useAuth().logout()` then `navigate({ to: '/login' })`.