Permanently delete a template record

Deletes the template identified by {id} and all of its column-mapping records from the data layer. This is a hard delete and cannot be undone.

When to use: Call this to retire a template that is no longer needed. Ensure no roster uploads still reference the template before deleting.

How: Supply {id} and the required tenant-id header. The template's existence is verified first; an unknown ID returns 404 without deleting anything.

Returns: 204 No Content on success; the response has no body. Only the data-layer records are removed - the template's GCS artifacts (template.csv, mappings.csv, schema.json) are left in place and remain reachable through any still-valid signed URLs until those expire. The operation is not idempotent: repeating it returns 404.