Delete a template version everywhere

Deletes the version everywhere: cancels its queued builds and removes the durable record and the host entry immediately, so the version is gone from listings and cannot be launched or built as soon as this returns. The golden archive is removed from every registry after a grace period of about 30 minutes (computers launched from it may still stream it that long) — running computers are unaffected. Idempotent — a repeat returns 200 with deleted:true. The same version can be re-published with new content immediately.