n8n: add Fleet Ops endpoint to receive workflow error reports

New POST /api/v1/integrations/n8n/workflow-error, service-token
authenticated, for the central "Fleet Ops — Workflow Error Handler"
n8n workflow to report a bounded, secret-free failure (workflow id/
name, execution id, safe error category, trigger context, correlation
id, attempt, retry action). Idempotent on execution_id via the same
audit-event precheck pattern used by /return-callback, so a
redelivered error report is not registered twice.

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

backend/app/api/routers/integrations.py

@@ -13,7 +13,7 @@ from app.core.config import get_settings
 from app.core.errors import AppError
 from app.models.audit import AuditEvent
 from app.models.outbox import OutboxEvent
-from app.schemas import ScanResultOut
+from app.schemas import ScanResultOut, WorkflowErrorReportIn, WorkflowErrorReportResult
 from app.services.audit import record_audit_event
 from app.services.data_quality import run_scan
 
@@ -89,3 +89,60 @@ def scheduled_scan(
 
     result = run_scan(db, actor_label="n8n scheduled scan", actor_type="service")
     return ScanResultOut(created=result.created)
+
+
+@router.post("/workflow-error", response_model=WorkflowErrorReportResult)
+def workflow_error(
+    body: WorkflowErrorReportIn,
+    service_token: str = Header(..., alias="X-Service-Token"),
+    db: Session = Depends(get_db),
+) -> WorkflowErrorReportResult:
+    """Receives a bounded, secret-free failure report from the central n8n "Fleet Ops --
+    Workflow Error Handler" workflow, which is attached as the Error Workflow on every
+    other Fleet Ops n8n workflow. Idempotent on execution_id: n8n may redeliver the same
+    error report (e.g. after a timed-out response), so this must not double-record."""
+    if service_token != settings.n8n_callback_token:
+        raise AppError("UNAUTHORIZED_SERVICE", "Invalid service token.", status_code=401)
+
+    already_recorded = (
+        db.scalar(
+            select(AuditEvent.id).where(
+                AuditEvent.action == "n8n_workflow_failure_registered",
+                AuditEvent.metadata_json["execution_id"].astext == body.execution_id,
+            )
+        )
+        is not None
+    )
+    if not already_recorded:
+        correlation_id: uuid.UUID | None = None
+        if body.correlation_id:
+            try:
+                correlation_id = uuid.UUID(body.correlation_id)
+            except ValueError:
+                correlation_id = None
+        record_audit_event(
+            db,
+            actor_type="service",
+            actor_label="n8n error handler",
+            action="n8n_workflow_failure_registered",
+            entity_type="automation",
+            correlation_id=correlation_id,
+            after={
+                "workflow_id": body.workflow_id,
+                "workflow_name": body.workflow_name,
+                "error_category": body.error_category,
+                "error_summary": body.error_summary,
+                "trigger_context": body.trigger_context,
+                "attempt": body.attempt,
+                "retry_action": body.retry_action,
+                "failed_at": body.failed_at.isoformat(),
+            },
+            metadata={"execution_id": body.execution_id},
+        )
+        db.commit()
+
+    return WorkflowErrorReportResult(
+        status="already_registered" if already_recorded else "registered",
+        execution_id=body.execution_id,
+        occurred_at=datetime.now(UTC),
+    )