feat(demo): plain-language integration status, richer audit, reset integrity

Integration status badges across Dashboard/Automation now show honest
plain-language labels instead of raw backend state strings (and fix a
few states that had no matching CSS colour class at all). Audit trail
gets a "view related events" action reusing the existing correlation_id
filter. About page gains scope/architecture/security/testing sections
and a guided-demo entry point. POST /api/v1/demo/reset now runs and
records a server-side scenario-integrity check. Also fixes a second real
race condition (caught by the return-review e2e test): the odometer
scenario pre-fill now resolves before ReturnForm mounts instead of
patching its value in after the fact.

frontend/src/data/integrationLabels.ts

@@ -0,0 +1,18 @@
+import type { IntegrationStatus } from "../api/types";
+
+// Plain-language status per section 12 of the demo brief: a visitor shouldn't have to
+// decode raw backend state strings to tell whether an integration is actually working.
+// `statusClass` maps onto an existing `.status-*` CSS modifier so the badge keeps
+// correct colour-coding; `label` is the human-readable text shown instead of the raw value.
+export const N8N_STATE_META: Record<IntegrationStatus["n8n"]["state"], { statusClass: string; label: string }> = {
+  disabled: { statusClass: "not_configured", label: "Not connected" },
+  unavailable: { statusClass: "unavailable", label: "Delivery failed" },
+  degraded: { statusClass: "needs_attention", label: "Retry available" },
+  operational: { statusClass: "available", label: "Operational" },
+  no_evidence: { statusClass: "no_events", label: "Prepared" },
+};
+
+export const MCP_STATE_META: Record<IntegrationStatus["mcp_hub"]["state"], { statusClass: string; label: string }> = {
+  not_configured: { statusClass: "not_configured", label: "Not connected" },
+  configured: { statusClass: "no_events", label: "Prepared" },
+};