feat(proxmox): support node-level routes and journalctl access

This change enables Proxmox node-level operations without requiring a specific
LXC container VMID.

**Features added:**
- New `/proxmox/journalctl/{node}` API endpoint for streaming node journalctl
- Route configuration support for Proxmox nodes (VMID = 0)
- `ReverseLookupNode` function for node discovery by hostname/IP/alias
- `NodeJournalctl` method for executing journalctl on nodes

**Behavior changes:**
- VMID parameter in journalctl endpoints is now optional
- Routes targeting nodes (without specific containers) are now valid

**Bug fixes:**
- Fixed error message variable reference in route validation

internal/proxmox/client.go

@@ -147,6 +147,34 @@ func (c *Client) ReverseLookupResource(ip net.IP, hostname string, alias string)
 	return nil, ErrResourceNotFound
 }
 
+// ReverseLookupNode looks up a node by name or IP address.
+// Returns the node name if found.
+func (c *Client) ReverseLookupNode(hostname string, ip net.IP, alias string) string {
+	shouldCheckHostname := hostname != ""
+	shouldCheckIP := ip != nil && !ip.IsLoopback() && !ip.IsUnspecified()
+	shouldCheckAlias := alias != ""
+
+	if shouldCheckHostname {
+		hostname, _, _ = strings.Cut(hostname, ".")
+	}
+
+	for _, node := range c.Cluster.Nodes {
+		if shouldCheckHostname && node.Name == hostname {
+			return node.Name
+		}
+		if shouldCheckIP {
+			nodeIP := net.ParseIP(node.IP)
+			if nodeIP != nil && nodeIP.Equal(ip) {
+				return node.Name
+			}
+		}
+		if shouldCheckAlias && node.Name == alias {
+			return node.Name
+		}
+	}
+	return ""
+}
+
 // Key implements pool.Object
 func (c *Client) Key() string {
 	return c.Cluster.ID

internal/proxmox/node.go

@@ -186,3 +186,14 @@ func (n *Node) NodeCommand(ctx context.Context, command string) (io.ReadCloser,
 
 	return pr, nil
 }
+
+func (n *Node) NodeJournalctl(ctx context.Context, service string, limit int) (io.ReadCloser, error) {
+	command := "journalctl -f"
+	if service != "" {
+		command = fmt.Sprintf("journalctl -u %q -f", service)
+	}
+	if limit > 0 {
+		command = fmt.Sprintf("%s -n %d", command, limit)
+	}
+	return n.NodeCommand(ctx, command)
+}