Add course retrieval by share code feature and enhance course search functionality

- Implemented a new endpoint in VocabController to retrieve courses using a share code.
- Updated VocabService to include logic for validating share codes and checking course access permissions.
- Enhanced course listing functionality with search and language filtering options in the frontend.
- Added a dialog for users to input share codes and search for courses, improving user experience.
- Updated internationalization files to include new strings for share code functionality and search features.

backend/routers/vocabRouter.js

@@ -26,6 +26,7 @@ router.post('/chapters/:chapterId/vocabs', vocabController.addVocabToChapter);
 router.post('/courses', vocabController.createCourse);
 router.get('/courses', vocabController.getCourses);
 router.get('/courses/my', vocabController.getMyCourses);
+router.post('/courses/find-by-code', vocabController.getCourseByShareCode);
 router.get('/courses/:courseId', vocabController.getCourse);
 router.put('/courses/:courseId', vocabController.updateCourse);
 router.delete('/courses/:courseId', vocabController.deleteCourse);