feat(n8n): add scheduled quality-scan workflow

The original docs described two n8n workflows but the repository only ever
shipped one (return-processing); the sketched second workflow (knowledge
sync) depends on RAGcore, which isn't connected here, so it stays deferred.

Add POST /api/v1/integrations/n8n/scheduled-scan (X-Service-Token
protected, same pattern as the return callback), calling the same
run_scan() the manual "Run quality scan" UI action uses and recording a
service-actor data_quality_scan_run audit event. run_scan() already only
creates an issue for a condition without one open, so overlapping triggers
do no duplicate domain work.

n8n/mobilityops-scheduled-quality-scan.json (hourly schedule + manual test
trigger, both feeding the same HTTP call) ships "active": false so it can't
fire anywhere until deliberately published. Verified live against the
local n8n instance via the Manual test trigger: full green execution, and
the resulting data_quality_scan_run audit event (actor_type=service,
actor_label="n8n scheduled scan") confirms the real round trip, not just a
contract test. deploy/unraid/setup-scheduled-scan.sh mirrors the existing
return-workflow publish script for the shared Unraid n8n.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: up down logs test lint seed reset n8n-setup demo e2e
+.PHONY: up down logs test lint seed reset n8n-setup n8n-setup-scan demo e2e
 
 up:
 	docker compose up --build -d
@@ -32,6 +32,13 @@ n8n-setup:
 	docker compose exec n8n n8n publish:workflow --id=mobilityops-return-processing
 	docker compose restart n8n
 
+# One-time per environment: imports and activates the scheduled quality-scan workflow.
+# Same owner-account precondition as n8n-setup above.
+n8n-setup-scan:
+	docker compose exec n8n n8n import:workflow --input=//imports/mobilityops-scheduled-quality-scan.json
+	docker compose exec n8n n8n publish:workflow --id=mobilityops-scheduled-quality-scan
+	docker compose restart n8n
+
 # Full deterministic demo bootstrap: build, migrate (automatic on api startup), seed.
 demo: up
 	docker compose exec api python -m app.cli seed --reset