n8n: store cleaned workflow definitions as repo source of truth

Move the two live-validated workflows into n8n/workflows/ (credential-
based auth referenced by name only, no secret values), add a manifest
covering all 4 canonical workflows and a read-only drift-check script
against n8n's Public API. Retire the pre-integration root-level starter
files that still carried the literal-token pattern, and repoint the
Unraid deploy scripts, Makefile targets and runbook at the new files.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

FILE_INDEX.md

@@ -60,7 +60,10 @@
 - `knowledge/procedures/09-booking-conflicts.md`
 - `knowledge/procedures/10-roles-and-escalation.md`
 - `n8n/README.md`
-- `n8n/mobilityops-return-processing.json`
+- `n8n/workflows/MANIFEST.md`
+- `n8n/workflows/fleet-ops-vehicle-return.json`
+- `n8n/workflows/fleet-ops-data-quality-scan.json`
+- `n8n/workflows/check_drift.py`
 - `seed/README.md`
 - `seed/bookings.csv`
 - `seed/customers.csv`