feat(11-03): inject IBrandingService into all 5 export ViewModels and assemble branding in ExportHtmlAsync

- Add IBrandingService field and DI constructor parameter to all 5 ViewModels
- Add optional IBrandingService? parameter to test constructors (PermissionsViewModel, StorageViewModel, UserAccessAuditViewModel)
- Assemble ReportBranding from GetMspLogoAsync + _currentProfile.ClientLogo before each WriteAsync call
- Pass branding as last parameter to WriteAsync in all ExportHtmlAsync methods
- Guard clause: branding assembly skipped (branding = null) when _brandingService is null (test constructors)
- Build: 0 warnings, 0 errors; tests: 254 passed / 0 failed / 26 skipped

SharepointToolbox/ViewModels/Tabs/SearchViewModel.cs

@@ -17,6 +17,7 @@ public partial class SearchViewModel : FeatureViewModelBase
     private readonly ISessionManager _sessionManager;
     private readonly SearchCsvExportService _csvExportService;
     private readonly SearchHtmlExportService _htmlExportService;
+    private readonly IBrandingService _brandingService;
     private readonly ILogger<FeatureViewModelBase> _logger;
     private TenantProfile? _currentProfile;
 
@@ -59,6 +60,7 @@ public partial class SearchViewModel : FeatureViewModelBase
         ISessionManager sessionManager,
         SearchCsvExportService csvExportService,
         SearchHtmlExportService htmlExportService,
+        IBrandingService brandingService,
         ILogger<FeatureViewModelBase> logger)
         : base(logger)
     {
@@ -66,6 +68,7 @@ public partial class SearchViewModel : FeatureViewModelBase
         _sessionManager   = sessionManager;
         _csvExportService = csvExportService;
         _htmlExportService = htmlExportService;
+        _brandingService  = brandingService;
         _logger           = logger;
 
         ExportCsvCommand  = new AsyncRelayCommand(ExportCsvAsync,  CanExport);
@@ -168,7 +171,15 @@ public partial class SearchViewModel : FeatureViewModelBase
         if (dialog.ShowDialog() != true) return;
         try
         {
-            await _htmlExportService.WriteAsync(Results, dialog.FileName, CancellationToken.None);
+            ReportBranding? branding = null;
+            if (_brandingService is not null)
+            {
+                var mspLogo = await _brandingService.GetMspLogoAsync();
+                var clientLogo = _currentProfile?.ClientLogo;
+                branding = new ReportBranding(mspLogo, clientLogo);
+            }
+
+            await _htmlExportService.WriteAsync(Results, dialog.FileName, CancellationToken.None, branding);
             OpenFile(dialog.FileName);
         }
         catch (Exception ex) { StatusMessage = $"Export failed: {ex.Message}"; _logger.LogError(ex, "HTML export failed."); }