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/BulkResultCsvExportService.cs

@@ -3,6 +3,7 @@ using System.IO;
 using System.Text;
 using CsvHelper;
 using SharepointToolbox.Core.Models;
+using SharepointToolbox.Localization;
 
 namespace SharepointToolbox.Services.Export;
 
@@ -10,12 +11,13 @@ public class BulkResultCsvExportService
 {
     public string BuildFailedItemsCsv<T>(IReadOnlyList<BulkItemResult<T>> failedItems)
     {
+        var TL = TranslationSource.Instance;
         using var writer = new StringWriter();
         using var csv = new CsvWriter(writer, CultureInfo.InvariantCulture);
 
         csv.WriteHeader<T>();
-        csv.WriteField("Error");
-        csv.WriteField("Timestamp");
+        csv.WriteField(TL["report.col.error"]);
+        csv.WriteField(TL["report.col.timestamp"]);
         csv.NextRecord();
 
         foreach (var item in failedItems.Where(r => !r.IsSuccess))