Phase 7a: stable workflow id for the n8n import (AUD-115)

n8n 2.18.5 rejects an import whose workflow JSON has no `id`
(SQLITE_CONSTRAINT: NOT NULL constraint failed: workflow_entity.id). Give the
workflow a fixed id and record that the import -> publish -> active flow was
rehearsed in a throwaway n8n container before asking for approval.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

deploy/n8n-morning-brief.json

@@ -1,4 +1,5 @@
 {
+  "id": "schoolMorningBrf",
   "name": "Compass / NHS — 6:00am morning brief",
   "nodes": [
     {