feat(models): implement typed response models for PVE 8.x and 9.x

Add C# model classes for all PVE API resources: nodes, VMs, VM config,
containers, storage, network interfaces, SDN zones/vnets, users, roles,
permissions, snapshots, tasks, and cluster status. All models use dual
JSON attributes (System.Text.Json + Newtonsoft.Json), nullable optional
fields, and human-readable ToString() overrides.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/PSProxmoxVE.Core/Models/Vms/PveTaskLog.cs

@@ -0,0 +1,21 @@
+using Newtonsoft.Json;
+
+namespace PSProxmoxVE.Core.Models.Vms
+{
+    /// <summary>
+    /// Represents a single log line from a Proxmox VE task log,
+    /// as returned by the /nodes/{node}/tasks/{upid}/log endpoint.
+    /// </summary>
+    public class PveTaskLog
+    {
+        /// <summary>Line number (1-based).</summary>
+        [JsonProperty("n")]
+        public int LineNumber { get; set; }
+
+        /// <summary>Log line text.</summary>
+        [JsonProperty("t")]
+        public string Text { get; set; } = string.Empty;
+
+        public override string ToString() => $"{LineNumber,4}: {Text}";
+    }
+}