feat: host heartbeat status and dashboard metrics (2.2)

Track agent.heartbeat and report.daily.ssh per host; show online/stale
on Hosts UI; dashboard counters and SAC_HEARTBEAT_STALE_MINUTES config.

backend/app/api/v1/dashboards.py

@@ -6,9 +6,11 @@ from sqlalchemy import func, select
 from sqlalchemy.orm import Session, joinedload
 
 from app.auth.jwt_auth import get_current_user
+from app.config import get_settings
 from app.database import get_db
 from app.models import Event, Host, Problem
 from app.schemas.list_models import EventSummary
+from app.services.host_health import DAILY_REPORT_SSH, HEARTBEAT_TYPE, count_stale_hosts
 
 router = APIRouter(prefix="/dashboards", tags=["dashboards"])
 
@@ -16,6 +18,9 @@ router = APIRouter(prefix="/dashboards", tags=["dashboards"])
 class DashboardSummary(BaseModel):
     events_last_24h: int
     hosts_total: int
+    hosts_stale: int
+    heartbeats_24h: int
+    daily_reports_24h: int
     problems_open: int
     severity_24h: dict[str, int]
     recent_events: list[EventSummary]
@@ -32,6 +37,18 @@ def dashboard_summary(
         select(func.count()).select_from(Event).where(Event.received_at >= since)
     ) or 0
     hosts_total = db.scalar(select(func.count()).select_from(Host)) or 0
+    settings = get_settings()
+    hosts_stale = count_stale_hosts(db, settings.sac_heartbeat_stale_minutes)
+    heartbeats_24h = db.scalar(
+        select(func.count())
+        .select_from(Event)
+        .where(Event.received_at >= since, Event.type == HEARTBEAT_TYPE)
+    ) or 0
+    daily_reports_24h = db.scalar(
+        select(func.count())
+        .select_from(Event)
+        .where(Event.received_at >= since, Event.type == DAILY_REPORT_SSH)
+    ) or 0
     problems_open = (
         db.scalar(select(func.count()).select_from(Problem).where(Problem.status == "open")) or 0
     )
@@ -71,6 +88,9 @@ def dashboard_summary(
     return DashboardSummary(
         events_last_24h=events_24h,
         hosts_total=hosts_total,
+        hosts_stale=hosts_stale,
+        heartbeats_24h=heartbeats_24h,
+        daily_reports_24h=daily_reports_24h,
         problems_open=problems_open,
         severity_24h=severity_24h,
         recent_events=recent_events,

backend/app/api/v1/hosts.py

@@ -3,9 +3,16 @@ from sqlalchemy import func, select
 from sqlalchemy.orm import Session
 
 from app.auth.jwt_auth import get_current_user
+from app.config import get_settings
 from app.database import get_db
 from app.models import Event, Host
 from app.schemas.list_models import HostListResponse, HostSummary
+from app.services.host_health import (
+    DAILY_REPORT_SSH,
+    HEARTBEAT_TYPE,
+    agent_status,
+    max_event_time_by_host,
+)
 
 router = APIRouter(prefix="/hosts", tags=["hosts"])
 
@@ -37,11 +44,16 @@ def list_hosts(
         .limit(page_size)
     ).all()
 
+    settings = get_settings()
+    hb_map = max_event_time_by_host(db, HEARTBEAT_TYPE)
+    report_map = max_event_time_by_host(db, DAILY_REPORT_SSH)
+
     items: list[HostSummary] = []
     for host in rows:
         event_count = db.scalar(
             select(func.count()).select_from(Event).where(Event.host_id == host.id)
         )
+        last_hb = hb_map.get(host.id)
         items.append(
             HostSummary(
                 id=host.id,
@@ -53,6 +65,11 @@ def list_hosts(
                 ipv4=host.ipv4,
                 last_seen_at=host.last_seen_at,
                 event_count=int(event_count or 0),
+                last_heartbeat_at=last_hb,
+                last_daily_report_at=report_map.get(host.id),
+                agent_status=agent_status(
+                    last_hb, stale_minutes=settings.sac_heartbeat_stale_minutes
+                ),
             )
         )
 

backend/app/api/v1/stream.py

@@ -10,6 +10,8 @@ from sqlalchemy.orm import Session
 from app.auth.jwt_auth import verify_access_token
 from app.database import SessionLocal
 from app.models import Event, Problem
+from app.config import get_settings
+from app.services.host_health import DAILY_REPORT_SSH, HEARTBEAT_TYPE, count_stale_hosts
 from app.version import APP_VERSION
 
 router = APIRouter(prefix="/stream", tags=["stream"])
@@ -26,10 +28,24 @@ def _dashboard_snapshot(db: Session) -> dict:
         db.scalar(select(func.count()).select_from(Problem).where(Problem.status == "open")) or 0
     )
     last_event = db.scalar(select(Event.id).order_by(Event.received_at.desc()).limit(1))
+    settings = get_settings()
     return {
         "type": "dashboard",
         "version": APP_VERSION,
         "events_last_24h": events_24h,
+        "hosts_stale": count_stale_hosts(db, settings.sac_heartbeat_stale_minutes),
+        "heartbeats_24h": db.scalar(
+            select(func.count())
+            .select_from(Event)
+            .where(Event.received_at >= since, Event.type == HEARTBEAT_TYPE)
+        )
+        or 0,
+        "daily_reports_24h": db.scalar(
+            select(func.count())
+            .select_from(Event)
+            .where(Event.received_at >= since, Event.type == DAILY_REPORT_SSH)
+        )
+        or 0,
         "problems_open": problems_open,
         "last_event_id": last_event,
         "at": datetime.now(timezone.utc).isoformat(),