Add per-node health checks with status indicators and scheduled probes.

service/cmd/server/main.go

@@ -57,6 +57,9 @@ func main() {
 	if app.Executor != nil {
 		app.Executor.StopScheduler()
 	}
+	if app.HealthChecker != nil {
+		app.HealthChecker.StopScheduler()
+	}
 
 	shutdownContext, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()