feat: add Departments management page with tree + user list

apps/admin/src/App.tsx

@@ -26,6 +26,7 @@ import PermissionsPage from './pages/Permissions';
 import AttendancePage from './pages/Attendance';
 import TeacherWorkspacePage from './pages/TeacherWorkspace';
 import NotificationsPage from './pages/Notifications';
+import DepartmentsPage from './pages/Departments';
 import PermissionRoute from './components/PermissionRoute';
 
 const PrivateRoute: React.FC<{ children: React.ReactNode }> = ({ children }) => {
@@ -233,6 +234,15 @@ const App: React.FC = () => {
               />
 
               <Route path="notifications" element={<NotificationsPage />} />
+
+              <Route
+                path="departments"
+                element={
+                  <PermissionRoute permission="department:view">
+                    <DepartmentsPage />
+                  </PermissionRoute>
+                }
+              />
             </Route>
           </Routes>
         </BrowserRouter>