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/Services/IUserAccessAuditService.cs

@@ -22,6 +22,7 @@ public interface IUserAccessAuditService
     /// <returns>Flat list of access entries for the target users.</returns>
     Task<IReadOnlyList<UserAccessEntry>> AuditUsersAsync(
         ISessionManager sessionManager,
+        TenantProfile currentProfile,
         IReadOnlyList<string> targetUserLogins,
         IReadOnlyList<SiteInfo> sites,
         ScanOptions options,

SharepointToolbox/Services/UserAccessAuditService.cs

@@ -24,6 +24,7 @@ public class UserAccessAuditService : IUserAccessAuditService
 
     public async Task<IReadOnlyList<UserAccessEntry>> AuditUsersAsync(
         ISessionManager sessionManager,
+        TenantProfile currentProfile,
         IReadOnlyList<string> targetUserLogins,
         IReadOnlyList<SiteInfo> sites,
         ScanOptions options,
@@ -53,7 +54,7 @@ public class UserAccessAuditService : IUserAccessAuditService
             var profile = new TenantProfile
             {
                 TenantUrl = site.Url,
-                ClientId = string.Empty, // Will be set by SessionManager from cached session
+                ClientId = currentProfile.ClientId,
                 Name = site.Title
             };