- Navbar: responsive nav with ShieldAI logo, nav links, auth buttons,
mobile hamburger menu, theme toggle, scroll-aware glass effect
- Footer: multi-column responsive layout with product/company/resources/
legal links, social icons, copyright bar
- PageContainer: centered wrapper with max-w-7xl and responsive padding
- AppShell: root layout composing Navbar + main + Footer with dot-grid
background and MetaProvider
- useAuth stub hook for future auth integration (task 23)
- Wire AppShell into app.tsx as Router root
- Unit tests for PageContainer and useAuth
