feat: emit native types instead of Newtonsoft JObject/JArray in public APIs

Replace all Newtonsoft.Json.Linq types (JObject, JArray, JToken) exposed
in public service methods, model properties, and cmdlet OutputTypes with
native .NET types (Dictionary<string, object?>, List<Dictionary<string,
object?>>, PSObject).

New utilities:
- JsonHelper: ToNative, ToDictionary, ToListOfDictionaries for recursive
  JToken→native conversion
- NativeListConverter / NativeDictionaryConverter: JsonConverters for
  model properties that deserialize JArray/JObject to native types

Services updated (8 methods):
- NodeService: GetNodeConfig, GetNodeDns → Dictionary<string, object?>
- BackupService: GetNotBackedUp → List<Dictionary<string, object?>>
- ClusterConfigService: GetClusterConfig, GetTotem, GetQdevice → Dictionary
- HaService: GetManagerStatus → Dictionary<string, object?>
- VmService: GetGuestExecStatus → Dictionary<string, object?>

Models updated (2 properties):
- PvePool.Members: JArray → List<Dictionary<string, object?>>
- PveHaRule.Properties: JObject → Dictionary<string, object?>

Cmdlets updated (5):
- GetPveClusterConfigCmdlet: OutputType JToken → Dictionary<string, object>
- GetPveNodeConfigCmdlet: iteration updated for Dictionary
- GetPveNodeDnsCmdlet: iteration updated for Dictionary
- GetPveBackupInfoCmdlet: iteration updated for List<Dictionary>
- InvokePveVmGuestExecCmdlet: polling updated for Dictionary

Added D013 to DECISIONS.md: cmdlets must emit only native or module-defined types.

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

src/PSProxmoxVE.Core/Models/Cluster/PvePool.cs

@@ -1,5 +1,6 @@
+using System.Collections.Generic;
 using Newtonsoft.Json;
-using Newtonsoft.Json.Linq;
+using PSProxmoxVE.Core.Utilities;
 
 namespace PSProxmoxVE.Core.Models.Cluster;
 
@@ -21,11 +22,12 @@ public class PvePool
     public string? Comment { get; set; }
 
     /// <summary>
-    /// The pool members (VMs, containers, storage). Returned as a raw array
+    /// The pool members (VMs, containers, storage). Returned as a list of dictionaries
     /// when querying a specific pool.
     /// </summary>
     [JsonProperty("members")]
-    public JArray? Members { get; set; }
+    [JsonConverter(typeof(NativeListConverter))]
+    public List<Dictionary<string, object?>>? Members { get; set; }
 
     /// <inheritdoc />
     public override string ToString()