Initial Release

Feature: implement local favorites using Room database

- Add Room database, DAO, and Entity to the core module for persistent storage of favorite courses.
- Introduce `CourseRepository` to manage data flow between network and local storage.
- Implement `FavoritesViewModel` and `FavoritesActivity` to display saved courses.
- Update `HomeViewModel` to combine remote course data with local favorites status using Coroutine flows.
- Enhance `CourseDetailActivity` to allow adding/removing courses from favorites.
- Update UI and adapters to reflect favorite status with new icons and color states.
- Configure Koin dependencies for the new repository, database, and view models.