Editing a work order's POC never reached the backend: no update path wrote
PocName/PocPhone/PocNotes, so the optimistic UI edit was lost on refetch and
the completion freeze captured the Site contact instead of the manual value,
and nothing was audited.
- Add tenant-scoped PATCH api/workorders/{id}/poc via new WorkOrderPocService
+ WorkOrderPocDataService: persists the override, stages FieldChanged audit
entries (which also write field locks so sync never overwrites a manual POC),
and enforces row-version concurrency and terminal-status read-only rules.
- Lock semantics (SH-190): a manual POC away from the Site's live contacts is
stored WO-level; an edit equal to a live Site contact (or blanking name+phone)
stores nothing so the WO follows the Site. PocCustomized exposes the state.
- Board projection, completion freeze and create now share one Site-contact
fallback (first non-deleted contact by SiteContactOrder) so a never-overridden
WO keeps following the Site, including at create when the wizard prefills it.
- Route contract baseline gains PATCH {id:int}/poc.
