Implement vocab course and grammar exercise features in backend and frontend

- Added new course management functionalities in VocabController, including creating, updating, and deleting courses and lessons.
- Implemented enrollment and progress tracking for courses, along with grammar exercise creation and management.
- Updated database schema to include tables for courses, lessons, enrollments, and grammar exercises.
- Enhanced frontend with new routes and views for course listing and details, including internationalization support for course-related texts.
- Improved user experience by adding navigation to courses from the main vocab trainer view.

backend/routers/vocabRouter.js

@@ -22,6 +22,37 @@ router.get('/chapters/:chapterId', vocabController.getChapter);
 router.get('/chapters/:chapterId/vocabs', vocabController.listChapterVocabs);
 router.post('/chapters/:chapterId/vocabs', vocabController.addVocabToChapter);
 
+// Courses
+router.post('/courses', vocabController.createCourse);
+router.get('/courses', vocabController.getCourses);
+router.get('/courses/my', vocabController.getMyCourses);
+router.get('/courses/:courseId', vocabController.getCourse);
+router.put('/courses/:courseId', vocabController.updateCourse);
+router.delete('/courses/:courseId', vocabController.deleteCourse);
+
+// Lessons
+router.post('/courses/:courseId/lessons', vocabController.addLessonToCourse);
+router.put('/lessons/:lessonId', vocabController.updateLesson);
+router.delete('/lessons/:lessonId', vocabController.deleteLesson);
+
+// Enrollment
+router.post('/courses/:courseId/enroll', vocabController.enrollInCourse);
+router.delete('/courses/:courseId/enroll', vocabController.unenrollFromCourse);
+
+// Progress
+router.get('/courses/:courseId/progress', vocabController.getCourseProgress);
+router.put('/lessons/:lessonId/progress', vocabController.updateLessonProgress);
+
+// Grammar Exercises
+router.get('/grammar/exercise-types', vocabController.getExerciseTypes);
+router.post('/lessons/:lessonId/grammar-exercises', vocabController.createGrammarExercise);
+router.get('/lessons/:lessonId/grammar-exercises', vocabController.getGrammarExercisesForLesson);
+router.get('/lessons/:lessonId/grammar-exercises/progress', vocabController.getGrammarExerciseProgress);
+router.get('/grammar-exercises/:exerciseId', vocabController.getGrammarExercise);
+router.post('/grammar-exercises/:exerciseId/check', vocabController.checkGrammarExerciseAnswer);
+router.put('/grammar-exercises/:exerciseId', vocabController.updateGrammarExercise);
+router.delete('/grammar-exercises/:exerciseId', vocabController.deleteGrammarExercise);
+
 export default router;