feat(proxmox): better node-level routes auto-discovery with pointer VMID

- Add BaseURL field to Client for node-level route configuration
- Change VMID from int to *int to support three states:
  - nil: auto-discover node or VM from hostname/IP/alias
  - 0: node-level route (direct to Proxmox node API)
  - >0: LXC/QEMU resource route with container control
- Change Service string to Services []string for multi-service support
- Implement proper node-level route handling: HTTPS scheme,
  hostname from node BaseURL, default port 8006
- Move initial UpdateResources call to Init before starting loop
- Move proxmox auto-discovery earlier in route validation

BREAKING: NodeConfig.VMID is now a pointer type; NodeConfig.Service
renamed to Services (backward compatible via alias)

internal/proxmox/node.go

@@ -10,10 +10,10 @@ import (
 )
 
 type NodeConfig struct {
-	Node    string `json:"node" validate:"required"`
-	VMID    int    `json:"vmid" validate:"required"`
-	VMName  string `json:"vmname,omitempty"`
-	Service string `json:"service,omitempty"`
+	Node     string   `json:"node"`
+	VMID     *int     `json:"vmid"` // unset: auto discover; explicit 0: node-level route; >0: lxc/qemu resource route
+	VMName   string   `json:"vmname,omitempty"`
+	Services []string `json:"services,omitempty" aliases:"service"`
 } // @name ProxmoxNodeConfig
 
 type Node struct {