feat: live последние события на Dashboard; retention, health, runbook

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/api/v1/health.py

@@ -1,8 +1,11 @@
 from fastapi import APIRouter, Depends
-from sqlalchemy import text
+from sqlalchemy import func, select, text
 from sqlalchemy.orm import Session
 
+from app.config import get_settings
 from app.database import get_db
+from app.models import Event
+from app.services.host_health import count_stale_hosts
 from app.version import APP_NAME, APP_VERSION
 
 router = APIRouter(tags=["health"])
@@ -14,12 +17,28 @@ def build_health_payload(db: Session) -> dict:
         db.execute(text("SELECT 1"))
     except Exception:
         db_status = "error"
+
+    hosts_stale = 0
+    last_event_received_at: str | None = None
+    if db_status == "ok":
+        settings = get_settings()
+        hosts_stale = count_stale_hosts(db, settings.sac_heartbeat_stale_minutes)
+        last_received = db.scalar(select(func.max(Event.received_at)))
+        if last_received is not None:
+            last_event_received_at = last_received.isoformat()
+
+    overall = "ok" if db_status == "ok" else "degraded"
+    if db_status == "ok" and hosts_stale > 0:
+        overall = "degraded"
+
     return {
-        "status": "ok" if db_status == "ok" else "degraded",
+        "status": overall,
         "database": db_status,
         "service": "security-alert-center",
         "name": APP_NAME,
         "version": APP_VERSION,
+        "hosts_stale": hosts_stale,
+        "last_event_received_at": last_event_received_at,
     }