Introduce AuditLog model to track system-wide user actions including authentication, course management, file operations, and user account changes. Add AuditAction enum with 17 action types (CREATE, UPDATE, DELETE, LOGIN, LOGOUT, ENROLL, UNENROLL, SUBMIT_QUIZ, APPROVE_COURSE, REJECT_COURSE, UPLOAD_FILE, DELETE_FILE, CHANGE_PASSWORD, RESET_PASSWORD, VERIFY_EMAIL, DEACTIVATE_USER, ACTIVATE_USER). Include fields
Add is_skippable boolean field to Quiz schema, update quiz creation and update logic to handle the new field, and include it in student course content responses. Update seed data and type definitions accordingly.
