feat: close API coverage gaps — 51 new cmdlets across 6 areas

Phase 1 — Missing Update/Set operations (10 cmdlets):
- SDN: Set-PveSdnZone/Vnet/Subnet/Controller/Ipam/Dns + Invoke-PveSdnApply
- Set-PveRole, Set-PveStorage, Set-PveApiToken

Phase 2 — Cluster operations (8 cmdlets):
- Get-PveClusterResource (cluster-wide inventory)
- Get-PveTaskList, Stop-PveTask
- Get/New/Set/Remove-PvePool
- Get-PveBackupInfo (unprotected VMs)

Phase 3 — VM & container gaps (14 cmdlets):
- Move-PveVmDisk, Remove-PveVmDisk
- Guest agent: Get-PveVmGuestOsInfo/FsInfo, Read/Write-PveVmGuestFile,
  Set-PveVmGuestPassword, Invoke-PveVmGuestFsTrim
- Suspend/Resume-PveContainer, Resize-PveContainerDisk,
  New-PveContainerTemplate, Move-PveContainerVolume,
  Get-PveContainerInterface

Phase 4 — Storage content management (4 cmdlets):
- Get-PveStorageStatus, Remove/Set-PveStorageContent, New-PveStorageDisk

Phase 5 — Node operations (6 cmdlets):
- Get/Set-PveNodeConfig, Get/Set-PveNodeDns, Start/Stop-PveNodeVms

Phase 6 — Access management (9 cmdlets):
- Get/New/Set/Remove-PveGroup, Get/New/Set/Remove-PveDomain, Set-PvePassword

Total: 169 cmdlets (was 118). Includes models, services, format views,
Pester unit tests, manifest updates, README, CHANGELOG, API coverage docs.

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

src/PSProxmoxVE.Core/Models/Users/PveGroup.cs

@@ -0,0 +1,36 @@
+using System.Text.Json.Serialization;
+using Newtonsoft.Json;
+
+namespace PSProxmoxVE.Core.Models.Users;
+
+/// <summary>
+/// Represents a Proxmox VE group as returned by the /access/groups endpoint.
+/// </summary>
+public class PveGroup
+{
+    /// <summary>The unique group identifier.</summary>
+    [JsonPropertyName("groupid")]
+    [JsonProperty("groupid")]
+    public string GroupId { get; set; } = string.Empty;
+
+    /// <summary>Optional comment/description for the group.</summary>
+    [JsonPropertyName("comment")]
+    [JsonProperty("comment")]
+    public string? Comment { get; set; }
+
+    /// <summary>Comma-separated list of user IDs that belong to this group.</summary>
+    [JsonPropertyName("users")]
+    [JsonProperty("users")]
+    public string? Users { get; set; }
+
+    /// <summary>Array of member user IDs. Populated when available.</summary>
+    [JsonPropertyName("members")]
+    [JsonProperty("members")]
+    public string[]? Members { get; set; }
+
+    /// <inheritdoc />
+    public override string ToString()
+    {
+        return $"Group: {GroupId} | Comment: {Comment ?? "N/A"} | Users: {Users ?? "none"}";
+    }
+}