n8n: surface real per-workflow evidence on the integration status page

Fleet Ops integration status no longer depends only on a config
boolean or the most recent outbox event: N8nIntegrationStatus now
reports per-canonical-workflow evidence (last successful outbox
delivery for the return workflow, latest service-triggered
data_quality_scan_run for the scan workflow, latest
n8n_workflow_failure_registered for the error handler, and "not built"
for the still-blocked RAGcore sync), plus an error-handler summary
(total failures registered, latest failure + which workflow).

Automation page renders this as a localized workflow table (EN/NL/FR)
with technical workflow names tucked under a "Technical details"
disclosure, matching the existing progressive-disclosure pattern.

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

backend/app/schemas.py

@@ -223,6 +223,18 @@ class SearchResponse(BaseModel):
     results: list[SearchResultItem]
 
 
+class N8nWorkflowEvidence(BaseModel):
+    name: str
+    built: bool
+    last_seen_at: datetime | None
+
+
+class N8nErrorHandlerStatus(BaseModel):
+    total_failures_registered: int
+    latest_failure_at: datetime | None
+    latest_failure_workflow: str | None
+
+
 class N8nIntegrationStatus(BaseModel):
     configured: bool
     dispatch_enabled: bool
@@ -233,6 +245,10 @@ class N8nIntegrationStatus(BaseModel):
     succeeded: int
     latest_success_at: datetime | None
     latest_failure_at: datetime | None
+    expected_workflow_count: int
+    known_workflow_count: int
+    workflows: list[N8nWorkflowEvidence]
+    error_handler: N8nErrorHandlerStatus
 
 
 class McpHubIntegrationStatus(BaseModel):