Add attendance tracker migrations: session columns, qr_token, attendance_manual_code

• V1_147: add course_id, activated_by_id, start_time, end_time, active to professor_class_session
• V1_148: rename arrival_time→scanned_at, add status and device_id to student_attendance
• V1_149: create qr_token table
• V1_150: create attendance_manual_code table (renamed from manual_code for clarity)