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/api/handler.go

@@ -142,6 +142,7 @@ func NewHandler(requireAuth bool) *gin.Engine {
 
 		proxmox := v1.Group("/proxmox")
 		{
+			proxmox.GET("/journalctl/:node", proxmoxApi.Journalctl)
 			proxmox.GET("/journalctl/:node/:vmid", proxmoxApi.Journalctl)
 			proxmox.GET("/journalctl/:node/:vmid/:service", proxmoxApi.Journalctl)
 			proxmox.GET("/stats/:node/:vmid", proxmoxApi.Stats)