fix: reduce API calls to prevent syslog spam on non-clustered nodes (#322)

- Cache nodes list in pollPVEInstance and pass to sub-functions
- Prevents multiple GetNodes() calls per polling cycle
- Reduces API calls from ~5 per cycle to 1 per cycle
- Fixes syslog spam on standalone PVE nodes trying to find cluster certificates
- Fixes PBS 'Transport endpoint not connected' errors from excessive polling

Previously we were calling GetNodes() in:
- pollPVEInstance (main)
- pollVMs
- pollContainers
- pollStorage
- pollStorageBackups

Now we call it once and pass the list to avoid duplicate API calls that trigger
certificate checks on non-clustered nodes.

internal/monitoring/monitor.go

@@ -798,11 +798,12 @@ func (m *Monitor) pollPVEInstance(ctx context.Context, instanceName string, clie
 			// Try to use efficient cluster/resources endpoint
 			if !m.pollVMsAndContainersEfficient(ctx, instanceName, client) {
 				// Fall back to old method if cluster/resources fails
+				// Use WithNodes versions to avoid duplicate GetNodes calls
 				if instanceCfg.MonitorVMs {
-					m.pollVMs(ctx, instanceName, client)
+					m.pollVMsWithNodes(ctx, instanceName, client, nodes)
 				}
 				if instanceCfg.MonitorContainers {
-					m.pollContainers(ctx, instanceName, client)
+					m.pollContainersWithNodes(ctx, instanceName, client, nodes)
 				}
 			}
 		}
@@ -814,7 +815,7 @@ func (m *Monitor) pollPVEInstance(ctx context.Context, instanceName string, clie
 		case <-ctx.Done():
 			return
 		default:
-			m.pollStorage(ctx, instanceName, client)
+			m.pollStorageWithNodes(ctx, instanceName, client, nodes)
 		}
 	}
 
@@ -840,8 +841,8 @@ func (m *Monitor) pollPVEInstance(ctx context.Context, instanceName string, clie
 				// Poll backup tasks
 				m.pollBackupTasks(backupCtx, instanceName, client)
 
-				// Poll storage backups
+				// Poll storage backups - pass nodes to avoid duplicate API calls
-				m.pollStorageBackups(backupCtx, instanceName, client)
+				m.pollStorageBackupsWithNodes(backupCtx, instanceName, client, nodes)
 
 				// Poll guest snapshots
 				m.pollGuestSnapshots(backupCtx, instanceName, client)
@@ -997,6 +998,11 @@ func (m *Monitor) pollVMs(ctx context.Context, instanceName string, client PVECl
 		return
 	}
 
+	m.pollVMsWithNodes(ctx, instanceName, client, nodes)
+}
+
+// pollVMsWithNodes polls VMs using a provided nodes list to avoid duplicate GetNodes calls
+func (m *Monitor) pollVMsWithNodes(ctx context.Context, instanceName string, client PVEClientInterface, nodes []proxmox.Node) {
 	var allVMs []models.VM
 	for _, node := range nodes {
 		vms, err := client.GetVMs(ctx, node.Node)
@@ -1133,6 +1139,12 @@ func (m *Monitor) pollContainers(ctx context.Context, instanceName string, clien
 		return
 	}
 
+	m.pollContainersWithNodes(ctx, instanceName, client, nodes)
+}
+
+// pollContainersWithNodes polls containers using a provided nodes list to avoid duplicate GetNodes calls
+func (m *Monitor) pollContainersWithNodes(ctx context.Context, instanceName string, client PVEClientInterface, nodes []proxmox.Node) {
+
 	var allContainers []models.Container
 	for _, node := range nodes {
 		containers, err := client.GetContainers(ctx, node.Node)
@@ -1248,6 +1260,12 @@ func (m *Monitor) pollStorage(ctx context.Context, instanceName string, client P
 		return
 	}
 
+	m.pollStorageWithNodes(ctx, instanceName, client, nodes)
+}
+
+// pollStorageWithNodes polls storage using a provided nodes list to avoid duplicate GetNodes calls
+func (m *Monitor) pollStorageWithNodes(ctx context.Context, instanceName string, client PVEClientInterface, nodes []proxmox.Node) {
+
 	// Get cluster storage configuration for shared/enabled status
 	clusterStorages, err := client.GetAllStorage(ctx)
 	if err != nil {
@@ -1695,6 +1713,12 @@ func (m *Monitor) pollStorageBackups(ctx context.Context, instanceName string, c
 		return
 	}
 
+	m.pollStorageBackupsWithNodes(ctx, instanceName, client, nodes)
+}
+
+// pollStorageBackupsWithNodes polls backups using a provided nodes list to avoid duplicate GetNodes calls
+func (m *Monitor) pollStorageBackupsWithNodes(ctx context.Context, instanceName string, client PVEClientInterface, nodes []proxmox.Node) {
+
 	var allBackups []models.StorageBackup
 	seenVolids := make(map[string]bool) // Track seen volume IDs to avoid duplicates