refactor: update user roles, clean up admin settings UI, and adjust dashboard navigation logic

src/app/page.tsx

@@ -20,8 +20,8 @@ export default function LandingPage() {
       sessionStorage.setItem('userName', user.name);
       
       switch (user.role) {
-        case 'admin':
-        case 'manager':
+        case 'super_admin':
+        case 'admin_manager':
         case 'staff':
           router.push('/admin');
           break;