fix: prevent syslog spam on standalone Proxmox nodes

- Only check cluster status during initial configuration, not during polling
- Cache cluster membership in config to avoid repeated API calls
- Skip cluster/resources endpoint entirely for standalone nodes
- Change cluster detection failure from WARN to DEBUG (expected for standalone)

This addresses #322 where standalone PVE nodes were causing certificate
lookup errors in syslog every minute during polling.

internal/api/config_handlers.go

@@ -149,9 +149,11 @@ func detectPVECluster(clientConfig proxmox.ClientConfig, nodeName string) (isClu
 	defer cancel()
 	
 	// Get full cluster status to find the actual cluster name
+	// Note: This can cause certificate lookup errors on standalone nodes, but it's only done once during configuration
 	clusterStatus, err := tempClient.GetClusterStatus(ctx)
 	if err != nil {
-		log.Warn().Err(err).Msg("Failed to get cluster status")
+		// This is expected for standalone nodes - they will return an error when accessing cluster endpoints
+		log.Debug().Err(err).Msg("Could not get cluster status - likely a standalone node")
 		return false, "", nil
 	}
 	

internal/monitoring/monitor.go

@@ -856,16 +856,31 @@ 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
+	// Get instance config to check if this is configured as a cluster
+	var instanceCfg *config.PVEInstance
+	for _, cfg := range m.config.PVEInstances {
+		if cfg.Name == instanceName {
+			instanceCfg = &cfg
+			break
+		}
+	}
+	
+	// If not configured as a cluster, don't even try cluster endpoints
+	if instanceCfg == nil || !instanceCfg.IsCluster {
+		log.Debug().Str("instance", instanceName).Bool("isCluster", instanceCfg != nil && instanceCfg.IsCluster).Msg("Instance not configured as cluster, using traditional polling")
+		return false
+	}
+	
+	// For cluster configurations, verify it's still a cluster
+	// This check is cached in the configuration, so we avoid repeated API calls
 	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")
+		log.Debug().Err(err).Str("instance", instanceName).Msg("Could not verify 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")
+		log.Debug().Str("instance", instanceName).Msg("Configured as cluster but node reports not in a cluster, using traditional polling")
 		return false
 	}