Add Class and Session Scheduling System

Introduce a Class Scheduling System that allows tutors and admins to schedule sessions for each batch or course. The feature will support both one-time and recurring sessions, specifying details such as date, time, duration, tutor, and mode (online/offline). Integration with calendars and notifications (email, WhatsApp, or in-app) will ensure that students and tutors are reminded automatically. This system will also lay the foundation for attendance tracking and timetable views.