Customer letters

A letter tells a customer which of their drives were destroyed, with the certificate details. Managers make them.

1. New letter → pick the customer.
2. Choose the drives by certificate (tick one or more) or by date range.
3. Preview shows exactly what the PDF will look like (logo and signer from Admin → Letter branding).
4. Issue letter: the app numbers it (LTR-2026-0031), makes and keeps the PDF, and files it in SharePoint under Customer Letters/<customer>/<year>/.

The list shows every letter with its PDF. A letter whose drives were later moved to another customer is flagged, so you can issue a corrected one.