refactor: remove redundant System.Text.Json attributes from models

The codebase uses Newtonsoft.Json (JObject.Parse + ToObject<T>) exclusively.
Removed all [JsonPropertyName] attributes and [System.Text.Json.Serialization.
JsonIgnore] attributes from 41 model files, along with the now-unused
using System.Text.Json.Serialization imports. [JsonProperty] (Newtonsoft)
attributes remain as the sole serialization annotations.

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

src/PSProxmoxVE.Core/Models/Firewall/PveFirewallAlias.cs

@@ -1,4 +1,3 @@
-using System.Text.Json.Serialization;
 using Newtonsoft.Json;
 
 namespace PSProxmoxVE.Core.Models.Firewall;
@@ -12,21 +11,18 @@ public class PveFirewallAlias
     /// <summary>
     /// The alias name.
     /// </summary>
-    [JsonPropertyName("name")]
     [JsonProperty("name")]
     public string Name { get; set; } = string.Empty;
 
     /// <summary>
     /// The CIDR network or IP address (e.g. "10.0.0.0/8" or "192.168.1.1").
     /// </summary>
-    [JsonPropertyName("cidr")]
     [JsonProperty("cidr")]
     public string Cidr { get; set; } = string.Empty;
 
     /// <summary>
     /// Optional comment describing the alias.
     /// </summary>
-    [JsonPropertyName("comment")]
     [JsonProperty("comment")]
     public string? Comment { get; set; }