- Added a new JSONB field `lessonState` to the VocabCourseProgress model to store detailed lesson state information.
- Implemented methods in VocabService for sanitizing and serializing lesson state, ensuring robust data handling.
- Updated VocabLessonView to manage lesson state persistence, including local storage and server synchronization, improving user experience during vocabulary lessons.
- Introduced mechanisms for exporting and normalizing exercise answers, enhancing the accuracy of saved progress.
- 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.
