fix(07): fix people picker selection and audit service authentication

People picker ListBox used MouseBinding which fires before SelectedItem
updates, causing null CommandParameter. Replaced with SelectionChanged
event handler in code-behind.

AuditUsersAsync created TenantProfile with empty ClientId, causing
ArgumentException in SessionManager. Added currentProfile parameter
to pass the authenticated tenant's ClientId through.

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

SharepointToolbox/ViewModels/Tabs/UserAccessAuditViewModel.cs

@@ -229,8 +229,15 @@ public partial class UserAccessAuditViewModel : FeatureViewModelBase
             FolderDepth: 1,
             IncludeSubsites: IncludeSubsites);
 
+        if (_currentProfile == null)
+        {
+            StatusMessage = "No tenant profile selected. Please connect first.";
+            return;
+        }
+
         var entries = await _auditService.AuditUsersAsync(
             _sessionManager,
+            _currentProfile,
             userLogins,
             effectiveSites,
             scanOptions,