chore: release v2.4

- Add theme system (Dark/Light palettes, ModernTheme, ThemeManager)
- Add InputDialog, Spinner common view
- Add DuplicatesCsvExportService
- Refresh views, dialogs, and view models across tabs
- Update localization strings (en/fr)
- Tweak services (transfer, permissions, search, user access, ownership elevation, bulk operations)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

SharepointToolbox/Services/IUserAccessAuditService.cs

@@ -27,5 +27,6 @@ public interface IUserAccessAuditService
         IReadOnlyList<SiteInfo> sites,
         ScanOptions options,
         IProgress<OperationProgress> progress,
-        CancellationToken ct);
+        CancellationToken ct,
+        Func<string, CancellationToken, Task<bool>>? onAccessDenied = null);
 }