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/Export/ReportSplitMode.cs

@@ -0,0 +1,16 @@
+namespace SharepointToolbox.Services.Export;
+
+/// <summary>How a report export is partitioned.</summary>
+public enum ReportSplitMode
+{
+    Single,
+    BySite,
+    ByUser
+}
+
+/// <summary>When a report is split, how HTML output is laid out.</summary>
+public enum HtmlSplitLayout
+{
+    SeparateFiles,
+    SingleTabbed
+}