- Add admin layout with sidebar navigation and session guard
- Create AdminSidebar client component with role-based nav links
- Add dashboard page showing stats (admin count, code counts)
- Add users management page (SuperAdmin only): list, create, delete,
and reset passwords for admin users
- Add codes management page: list all codes, generate new codes,
delete unused codes
- Add API routes for admin user CRUD (GET, POST, DELETE, PUT)
- Add API routes for code management (GET, POST, DELETE)
- All UI in Macedonian
