fix(metrics): refresh alert chain timestamp from durable evidence

apps/api/src/main.py

@@ -97,6 +97,7 @@ from src.routers import proposals as proposals_router
 # Legacy route imports (to be migrated)
 from src.routes import agent, notifications, pipelines, plugins
 from src.services.adr100_slo_metrics_service import get_adr100_slo_metrics_service
+from src.services.alert_chain_metrics_service import get_alert_chain_metrics_service
 from src.services.executor import close_executor
 from src.services.flywheel_stats_service import get_flywheel_stats_service
 
@@ -1025,6 +1026,15 @@ app.include_router(platform_v1.router, prefix="/api/v1/platform", tags=["AwoooP
 @app.get("/metrics", include_in_schema=False)
 async def prometheus_metrics() -> Response:
     """Prometheus metrics endpoint for alerting"""
+    # 2026-05-19 Codex — T85 Alert Chain DB evidence refresh.
+    # record_alert_chain_success() 是 process-local gauge；部署後第一個 scrape
+    # 可能尚未收到新 webhook，導致 smoke test 誤判 metric 不存在。
+    # 先用 AwoooP inbound / alert_operation_log 的 durable evidence 回填 last_success。
+    try:
+        await get_alert_chain_metrics_service().refresh_last_success_gauge()
+    except Exception as exc:
+        logger.warning("prometheus_metrics_alert_chain_evidence_error", error=str(exc))
+
     content = generate_latest().decode("utf-8")
     # 2026-05-07 ogt + Claude Sonnet 4.6 — INC-20260507-99ADF2 修復
     # 飛輪指標（awoooi_flywheel_*）原本只在 /api/v1/stats/flywheel/metrics 暴露，