📚 Course Endpoints

CRUD operations for courses (admin access required for some).

GET    /api/v1/courses                                # Get all courses
POST   /api/v1/courses                                # Create a new course (admin/instructor)
GET    /api/v1/courses/:id                            # Get course details
PUT    /api/v1/courses/:id                            # Update course (admin/instructor)
DELETE /api/v1/courses/:id                            # Delete course (admin/instructor)
GET    /api/v1/course/categoriesId/:categoryId        # Get courses for this category