- Created AppLayout.tsx with MUI AppBar + permanent sidebar drawer
- Grouped navigation: Overview, Fleet, Operations, Administration
- RBAC visibility: admin-only items (Users, Certificates, Settings)
- User menu with logout functionality
- Mobile-responsive collapsible drawer
- Active state indicator on current page
- Switched theme from lightTheme to darkTheme in App.tsx
- Wrapped authenticated routes in AppLayout with React Router Outlet
- 404 redirect to dashboard instead of placeholder page
