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/Users/PveRole.cs

@@ -0,0 +1,41 @@
+using System.Text.Json.Serialization;
+using Newtonsoft.Json;
+
+namespace PSProxmoxVE.Core.Models.Users;
+
+/// <summary>
+/// Represents a Proxmox VE role as returned by the /access/roles endpoint.
+/// Roles are named collections of privileges that can be assigned to users or groups via ACLs.
+/// </summary>
+public class PveRole
+{
+    /// <summary>
+    /// The unique role identifier (e.g., "Administrator", "PVEVMAdmin", "PVEDatastoreUser").
+    /// </summary>
+    [JsonPropertyName("roleid")]
+    [JsonProperty("roleid")]
+    public string RoleId { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Comma-separated list of privilege strings assigned to this role
+    /// (e.g., "VM.Allocate,VM.Config.Disk,Datastore.AllocateSpace").
+    /// </summary>
+    [JsonPropertyName("privs")]
+    [JsonProperty("privs")]
+    public string? Privileges { get; set; }
+
+    /// <summary>
+    /// Indicates whether this is a built-in / special role (1) that cannot be deleted,
+    /// or a custom role (0).
+    /// </summary>
+    [JsonPropertyName("special")]
+    [JsonProperty("special")]
+    public int? Special { get; set; }
+
+    /// <inheritdoc />
+    public override string ToString()
+    {
+        var specialStr = Special is 1 ? " [built-in]" : string.Empty;
+        return $"Role: {RoleId}{specialStr} | Privs: {Privileges ?? "none"}";
+    }
+}