feat(gateway): 创建/编辑网关后立即异步探活健康状态

- POST/PUT /api/gateways 成功后后台立即探活一次 /healthz 并覆盖落库，不阻塞请求
- probeAndRecordGateway 抽出单网关探活+落库复用；探活超时改为 var 供测试注入
- 网关页保存成功后延迟 2.5s 刷新一次，尽快展示最新健康状态
- 测试：立即探活、慢网关不阻塞、不可达落 unhealthy

internal/controlplane/api/hub_test.go

@@ -132,8 +132,35 @@ func (s *memoryStore) lock(key string) func() {
 	return lock.Unlock
 }
 
-func (s *memoryStore) CreateGateway(_ context.Context, _, _, _ string) (hub.Gateway, error) {
-	return hub.Gateway{}, nil
+func (s *memoryStore) CreateGateway(_ context.Context, name, endpoint, token string) (hub.Gateway, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if name == "" || token == "" {
+		return hub.Gateway{}, hub.ErrInvalid
+	}
+	if s.gateways == nil {
+		s.gateways = map[string]hub.Gateway{}
+	}
+	if _, exists := s.gateways[name]; exists {
+		return hub.Gateway{}, hub.ErrConflict
+	}
+	gateway := hub.Gateway{Name: name, Endpoint: endpoint, Token: token}
+	s.gateways[name] = gateway
+	return gateway, nil
+}
+
+func (s *memoryStore) RecordGatewayCheck(_ context.Context, name, status, reason string) (hub.Gateway, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	gateway, exists := s.gateways[name]
+	if !exists {
+		return hub.Gateway{}, hub.ErrNotFound
+	}
+	gateway.HealthStatus, gateway.LastCheckReason = status, reason
+	now := time.Now()
+	gateway.LastCheckedAt = &now
+	s.gateways[name] = gateway
+	return gateway, nil
 }
 func (s *memoryStore) UpdateGateway(_ context.Context, currentName, name, endpoint, token string) (hub.Gateway, error) {
 	s.mu.Lock()