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/Core/Models/DuplicateItem.cs

@@ -10,4 +10,8 @@ public class DuplicateItem
     public DateTime? Modified { get; set; }
     public int? FolderCount { get; set; }
     public int? FileCount { get; set; }
+    /// <summary>URL of the site the item was collected from.</summary>
+    public string SiteUrl { get; set; } = string.Empty;
+    /// <summary>Friendly site title; falls back to a derived label when unknown.</summary>
+    public string SiteTitle { get; set; } = string.Empty;
 }