feat(admin): add user vocab course management functionality

- Implemented `getUserVocabCourses` and `getVocabCourseForAdmin` methods in `AdminController` to allow admins to retrieve enrolled vocab courses for users and specific course details, respectively.
- Updated `adminRouter` to include new routes for accessing user vocab courses and course details.
- Enhanced `AdminService` with methods to list user-enrolled vocab courses and retrieve course information with lessons, ensuring proper access control.
- Improved `VocabService` to support the new functionalities, including attaching language names to course data.
- Updated UI components in `UsersView` to reflect changes, including error handling and loading states for course retrieval, along with localization updates for new features.

backend/routers/adminRouter.js

@@ -25,7 +25,9 @@ router.put('/users/:id/adult-verification', authenticate, adminController.setAdu
 router.get('/users/erotic-moderation', authenticate, adminController.getEroticModerationReports);
 router.get('/users/erotic-moderation/preview/:type/:targetId', authenticate, adminController.getEroticModerationPreview);
 router.put('/users/erotic-moderation/:id', authenticate, adminController.applyEroticModerationAction);
+router.get('/users/:id/vocab-courses', authenticate, adminController.getUserVocabCourses);
 router.post('/users/:id/vocab-lesson-progress/reset', authenticate, adminController.resetUserVocabLessonProgress);
+router.get('/vocab/courses/:courseId', authenticate, adminController.getVocabCourseForAdmin);
 router.get('/users/:id', authenticate, adminController.getUser);
 router.put('/users/:id', authenticate, adminController.updateUser);