feat(proxmox): add LXC container control endpoints

Add start, stop, and restart endpoints for LXC containers via the Proxmox API:
- POST /api/v1/proxmox/lxc/:node/:vmid/start
- POST /api/v1/proxmox/lxc/:node/:vmid/stop
- POST /api/v1/proxmox/lxc/:node/:vmid/restart

internal/api/v1/proxmox/common.go

@@ -0,0 +1,6 @@
+package proxmoxapi
+
+type ActionRequest struct {
+	Node string `uri:"node" binding:"required"`
+	VMID int    `uri:"vmid" binding:"required"`
+}