fix: prevent cluster/resources calls on non-clustered nodes

Non-clustered Proxmox nodes were getting certificate verification errors
when Pulse tried to use the cluster/resources endpoint. Now checks if
the node is actually in a cluster before attempting efficient polling.

internal/monitoring/monitor.go

@@ -38,6 +38,7 @@ type PVEClientInterface interface {
 	GetVMStatus(ctx context.Context, node string, vmid int) (*proxmox.VMStatus, error)
 	GetContainerStatus(ctx context.Context, node string, vmid int) (*proxmox.Container, error)
 	GetClusterResources(ctx context.Context, resourceType string) ([]proxmox.ClusterResource, error)
+	IsClusterMember(ctx context.Context) (bool, error)
 }
 
 // Monitor handles all monitoring operations
@@ -855,6 +856,19 @@ func (m *Monitor) pollPVEInstance(ctx context.Context, instanceName string, clie
 
 // pollVMsAndContainersEfficient uses the cluster/resources endpoint to get all VMs and containers in one call
 func (m *Monitor) pollVMsAndContainersEfficient(ctx context.Context, instanceName string, client PVEClientInterface) bool {
+	// First check if this is actually a cluster member
+	// Non-clustered nodes will trigger certificate errors when trying to use cluster/resources
+	isCluster, err := client.IsClusterMember(ctx)
+	if err != nil {
+		log.Debug().Err(err).Str("instance", instanceName).Msg("Could not determine cluster membership, falling back to traditional polling")
+		return false
+	}
+	
+	if !isCluster {
+		log.Debug().Str("instance", instanceName).Msg("Node is not in a cluster, using traditional polling")
+		return false
+	}
+	
 	log.Info().Str("instance", instanceName).Msg("Polling VMs and containers using cluster/resources")
 	
 	// Get all resources in a single API call

pkg/proxmox/cluster_client.go

@@ -619,6 +619,20 @@ func (cc *ClusterClient) GetContainerStatus(ctx context.Context, node string, vm
 	return result, err
 }
 
+// IsClusterMember checks if this node is part of a cluster
+func (cc *ClusterClient) IsClusterMember(ctx context.Context) (bool, error) {
+	var result bool
+	err := cc.executeWithFailover(ctx, func(client *Client) error {
+		isMember, err := client.IsClusterMember(ctx)
+		if err != nil {
+			return err
+		}
+		result = isMember
+		return nil
+	})
+	return result, err
+}
+
 // GetClusterHealthInfo returns detailed health information about the cluster
 func (cc *ClusterClient) GetClusterHealthInfo() models.ClusterHealth {
 	cc.mu.RLock()