feat: report where an update comes from and whether it is a security fix, refresh the index, read the host status

For netOrk MVP 5, on napalm-device-types 2.3.0:

- get_available_updates reads `apt list --upgradable` over the exec path
  (APT_UPGRADABLE_COMMAND), so each update carries its suite and security
  status; the APT API, which names only "Debian"/"Proxmox", is the fallback
  with security unknown. It raises when neither answers instead of returning
  [] -- it used to swallow every error.
- refresh_available_updates(): POST nodes/{n}/apt/update.
- HostStatusMixin over the exec path (reboot required, self-patching).

napalm_proxmox/driver.py

@@ -36,6 +36,7 @@ logger = logging.getLogger(__name__)
 
 from napalm_device_types import (
     FingerprintRule,
+    HostStatusMixin,
     HypervisorDriver,
     KernelFactsMixin,
     PortSpec,
@@ -84,6 +85,7 @@ class ProxmoxDriver(
     ProxmoxSystemMixin,
     KernelFactsMixin,
     SystemdServicesMixin,
+    HostStatusMixin,
     HypervisorDriver,
 ):
     """NAPALM driver for Proxmox VE nodes."""