feat: add get_system_config() — cluster name, timezone, node list

Implements get_system_config() in ProxmoxSystemMixin:
- cluster_name from /cluster/status (type=cluster entry)
- cluster_nodes list of online node hostnames
- timezone from /nodes/{node}/time
- hostname, ssh_port, ssh_password_auth with safe defaults

Used by NetOrk's sync task to name the NetBox Cluster after the
actual Proxmox cluster rather than falling back to the site name.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

napalm_proxmox/system_mixin.py

@@ -820,3 +820,47 @@ class ProxmoxSystemMixin:
             result[dev] = entry
 
         return result
+
+    def get_system_config(self) -> dict[str, Any]:
+        """Return system-level configuration for this Proxmox node.
+
+        Collected from ``/cluster/status`` and the node config API:
+
+        * ``cluster_name`` (str | None) — Proxmox cluster name; ``None`` when
+          the node is standalone (not part of a cluster).
+        * ``cluster_nodes`` (list[str]) — hostnames of all online cluster nodes.
+        * ``hostname`` (str) — this node's name as reported by the cluster.
+        * ``timezone`` (str | None) — e.g. ``"Europe/Berlin"``.
+        * ``ntp_servers`` (list[str]).
+        * ``ssh_port`` (int) — always 22 for Proxmox nodes.
+        * ``ssh_password_auth`` (bool) — ``False`` as a safe default.
+        """
+        cfg: dict[str, Any] = {
+            "cluster_name": None,
+            "cluster_nodes": [],
+            "hostname": self._node_name,
+            "timezone": None,
+            "ntp_servers": [],
+            "ssh_port": 22,
+            "ssh_password_auth": False,
+        }
+
+        # Cluster name and node list from /cluster/status
+        try:
+            status = self._api.cluster.status.get() or []
+            for entry in status:
+                if entry.get("type") == "cluster":
+                    cfg["cluster_name"] = entry.get("name")
+                elif entry.get("type") == "node" and entry.get("online"):
+                    cfg["cluster_nodes"].append(entry.get("name", ""))
+        except Exception as exc:
+            logger.debug("Failed to fetch cluster status for system config: %s", exc)
+
+        # Timezone from node time API
+        try:
+            time_cfg = self._node_api().time.get() or {}
+            cfg["timezone"] = time_cfg.get("timezone") or None
+        except Exception as exc:
+            logger.debug("Failed to fetch node time config: %s", exc)
+
+        return cfg