定期タスク設定

I need to set up several scheduled tasks on my Mac:

1. Daily at 2 AM: Backup ~/Documents to external drive
2. Every Monday 9 AM: Generate weekly report from ~/Data/logs/
3. Every 6 hours: Sync local folder with a remote server
4. First of month: Archive old files (>90 days) from ~/Downloads

Please:
- Generate the cron entries
- Create the shell scripts for each task
- Include error logging
- Save everything to ~/Scripts/scheduled/