feat: VM snapshots and reboot_host through the API

get_vm_snapshots, create_vm_snapshot, delete_vm_snapshot and
rollback_vm_snapshot for VMs and containers, so netOrk's snapshot view
works on Proxmox as it does on VMware. Proxmox lists the live state as a
pseudo-snapshot named "current"; it is never reported or addressable.
Containers have no RAM state, so include_memory is ignored for them.

reboot_host() restarts the node with POST /nodes/{node}/status
command=reboot instead of /sbin/reboot over SSH.

napalm_proxmox/vm_contract_mixin.py

@@ -182,3 +182,12 @@ class ProxmoxVMContractMixin:
         vmid, vm_type = self._resolve_vm(name)
         cfg = self._guest_api(vmid, vm_type).config.get() or {}
         return parse_vm_config(str(vmid), vm_type, cfg)
+
+    # -- the node itself --------------------------------------------------------
+
+    def reboot_host(self) -> None:
+        """Restart this Proxmox node through the API (no SSH involved)."""
+        try:
+            self._node_api().status.post(command="reboot")
+        except Exception as exc:
+            raise RuntimeError(f"Reboot of node {self._node_name!r} refused: {exc}") from exc