fix(ops): 同步 source provider freshness 告警規則

ops/monitoring/alerts-unified.yml

@@ -651,6 +651,24 @@ groups:
           summary: "2 小時內未收到任何告警 ({{ $labels.source }})"
           description: "可能是告警鏈路問題，請執行 Smoke Test"
 
+      - alert: SourceProviderIngestionStale
+        expr: |
+          time() - max by (source) (
+            awoooi_alert_chain_last_success_timestamp{source=~"sentry|signoz"}
+          ) > 86400
+        for: 15m
+        labels:
+          severity: warning
+          layer: k8s
+          component: source-ingestion
+          team: platform
+          auto_repair: "false"
+          alert_category: "alertchain_provider_freshness"
+        annotations:
+          summary: "{{ $labels.source }} source ingestion 超過 24 小時未更新"
+          description: "{{ $labels.source }} webhook endpoint 可能仍健康，但 AwoooP source dossier 已超過 24 小時沒有新事件。這是 provider ingestion / upstream smoke / correlation freshness 缺口，不是 Alertmanager 主鏈路故障。"
+          runbook: "先查 /api/v1/webhooks/{{ $labels.source }}/health，再查 /api/v1/platform/events/dossier/coverage?provider={{ $labels.source }}；若 endpoint OK 但 latest stale，檢查上游 Sentry/SignOz notification channel 或排程 smoke。"
+
       - alert: AlertChainUnhealthy
         expr: awoooi_alert_chain_healthy == 0
         for: 5m