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/OwnershipElevationService.cs

@@ -7,6 +7,17 @@ public class OwnershipElevationService : IOwnershipElevationService
 {
     public async Task ElevateAsync(ClientContext tenantAdminCtx, string siteUrl, string loginName, CancellationToken ct)
     {
+        // Tenant.SetSiteAdmin requires a real claims/UPN login; an empty string
+        // makes the server raise "Cannot convert Org ID to Claims" and abort.
+        // When the caller doesn't specify a user, fall back to the signed-in
+        // admin (the owner of tenantAdminCtx).
+        if (string.IsNullOrWhiteSpace(loginName))
+        {
+            tenantAdminCtx.Load(tenantAdminCtx.Web.CurrentUser, u => u.LoginName);
+            await tenantAdminCtx.ExecuteQueryAsync();
+            loginName = tenantAdminCtx.Web.CurrentUser.LoginName;
+        }
+
         var tenant = new Tenant(tenantAdminCtx);
         tenant.SetSiteAdmin(siteUrl, loginName, isSiteAdmin: true);
         await tenantAdminCtx.ExecuteQueryAsync();