fix: backup job creation requires vmid or -All, fix Enabled default

- Integration test: add -All to New-PveBackupJob call — PVE API
  requires either vmid or all when creating a backup job
- Fix New-PveBackupJob Enabled logic: jobs are enabled by default
  unless user explicitly passes -Enabled:$false (was broken because
  SwitchParameter default=true doesn't set IsPresent)
- Fix XML doc cref warning in NetworkService after RequireSdn removal

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

src/PSProxmoxVE.Core/Services/NetworkService.cs

@@ -11,7 +11,7 @@ namespace PSProxmoxVE.Core.Services
 {
     /// <summary>
     /// Service for Proxmox VE node network and SDN (Software-Defined Networking) API operations.
-    /// SDN methods require PVE 8.0 or later and will throw <see cref="PveVersionException"/> otherwise.
+    /// SDN methods require PVE 8.0 or later. Version checks are performed at the cmdlet layer.
     /// </summary>
     public class NetworkService
     {

src/PSProxmoxVE/Cmdlets/Backup/NewPveBackupJobCmdlet.cs

@@ -73,10 +73,10 @@ namespace PSProxmoxVE.Cmdlets.Backup
         public string? MailNotification { get; set; }
 
         /// <summary>
-        /// <para type="description">Whether the backup job is enabled. Default is true.</para>
+        /// <para type="description">Whether the backup job is enabled. Enabled by default unless -Enabled:$false is specified.</para>
         /// </summary>
-        [Parameter(Mandatory = false, HelpMessage = "Whether the backup job is enabled.")]
-        public SwitchParameter Enabled { get; set; } = true;
+        [Parameter(Mandatory = false, HelpMessage = "Whether the backup job is enabled. Default is enabled.")]
+        public SwitchParameter Enabled { get; set; }
 
         /// <summary>
         /// <para type="description">A comment or description for the backup job.</para>
@@ -102,7 +102,7 @@ namespace PSProxmoxVE.Cmdlets.Backup
             {
                 ["schedule"] = Schedule,
                 ["storage"] = Storage,
-                ["enabled"] = Enabled.IsPresent ? "1" : "0"
+                ["enabled"] = MyInvocation.BoundParameters.ContainsKey("Enabled") && !Enabled.IsPresent ? "0" : "1"
             };
 
             if (!string.IsNullOrEmpty(Mode)) config["mode"] = Mode!;

tests/PSProxmoxVE.Tests/Integration/Integration.Tests.ps1

@@ -1443,7 +1443,7 @@ Describe 'Integration Tests' -Tag 'Integration' {
     Context 'Backup Jobs' {
         It 'Should create a backup job' {
             Skip-IfNoTarget
-            { New-PveBackupJob -Schedule 'sat 03:00' -Storage $script:Storage -Mode snapshot -Comment 'pester-test-backup' -ErrorAction Stop } | Should -Not -Throw
+            { New-PveBackupJob -Schedule 'sat 03:00' -Storage $script:Storage -Mode snapshot -All -Comment 'pester-test-backup' -ErrorAction Stop } | Should -Not -Throw
         }
 
         It 'Should list backup jobs and find the test job' {