fix(grpc/server): mark node active on Subscribe and notify on status change

Optimistically mark node as online/active and persist ActiveAt when a node
subscribes, logging success or warning on failure. Send a node notification
in Pro mode if the status changed. Also tidy import ordering.

core/grpc/server/node_service_server.go

@@ -2,6 +2,9 @@ package server
 
 import (
 	"context"
+	"sync"
+	"time"
+
 	"github.com/crawlab-team/crawlab/core/constants"
 	"github.com/crawlab-team/crawlab/core/errors"
 	"github.com/crawlab-team/crawlab/core/interfaces"
@@ -15,8 +18,6 @@ import (
 	"go.mongodb.org/mongo-driver/bson"
 	"go.mongodb.org/mongo-driver/bson/primitive"
 	"go.mongodb.org/mongo-driver/mongo"
-	"sync"
-	"time"
 )
 
 var nodeServiceMutex = sync.Mutex{}
@@ -122,12 +123,31 @@ func (svr NodeServiceServer) Subscribe(request *grpc.NodeServiceSubscribeRequest
 		return err
 	}
 
+	// Optimistically mark node as active when subscription succeeds
+	// This provides fast recovery after reconnection while master monitor
+	// will verify health and revert if the connection is unstable
+	oldStatus := node.Status
+	node.Status = constants.NodeStatusOnline
+	node.Active = true
+	node.ActiveAt = time.Now()
+	err = service.NewModelService[models.Node]().ReplaceById(node.Id, *node)
+	if err != nil {
+		svr.Warnf("failed to update node status on subscribe: %v", err)
+		// Continue anyway - monitor will fix it
+	} else {
+		svr.Debugf("marked node[%s] as active on subscription (status: %s -> %s)",
+			request.NodeKey, oldStatus, node.Status)
+	}
+
 	// subscribe
 	nodeServiceMutex.Lock()
 	svr.subs[node.Id] = stream
 	nodeServiceMutex.Unlock()
 
-	// TODO: send notification
+	// send notification if status changed
+	if utils.IsPro() && oldStatus != node.Status {
+		go notification.GetNotificationService().SendNodeNotification(node)
+	}
 
 	// wait for stream to close
 	<-stream.Context().Done()