HostDesk v2.1.6 upgrade

1. Back up the database and current HostDesk files.
2. Upload/overwrite v2.1.6 files.
3. DO NOT overwrite/delete config.php or storage/installed.lock.
4. No new database column is required for this feature; it uses existing services.next_due_date and services.grace_until fields.
5. Open WHM Sync, sync/import accounts, then open Services -> Manage / Expiry for individual service dates.
6. Ensure cron/daily.php continues to run as before if you want grace-based automatic WHM suspension.

Permissions:
- Services View: can view service/manage screen.
- Services Edit: can save billing/expiry values.
- Services Execute: can provision/suspend/unsuspend/terminate in WHM.
