Version: 2026.08.04-force-mecca-timezone

- Forced PHP timezone to Asia/Riyadh in student, teacher, and admin exam pages.
- Forced the MySQL PDO session timezone to +03:00 in all three pages.
- Ensured exam input, display, NOW(), CURRENT_TIMESTAMP, scheduling, closing, retakes, and extensions share the same Mecca clock.
- Added automatic backup and rollback installer.
