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/Views/Common/Spinner.xaml.cs

@@ -0,0 +1,11 @@
+using System.Windows.Controls;
+
+namespace SharepointToolbox.Views.Common;
+
+public partial class Spinner : UserControl
+{
+    public Spinner()
+    {
+        InitializeComponent();
+    }
+}