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/ViewModels/Tabs/SettingsViewModel.cs

@@ -12,6 +12,7 @@ public partial class SettingsViewModel : FeatureViewModelBase
 {
     private readonly SettingsService _settingsService;
     private readonly IBrandingService _brandingService;
+    private readonly ThemeManager _themeManager;
 
     private string _selectedLanguage = "en";
     public string SelectedLanguage
@@ -39,6 +40,19 @@ public partial class SettingsViewModel : FeatureViewModelBase
         }
     }
 
+    private string _selectedTheme = "System";
+    public string SelectedTheme
+    {
+        get => _selectedTheme;
+        set
+        {
+            if (_selectedTheme == value) return;
+            _selectedTheme = value;
+            OnPropertyChanged();
+            _ = ApplyThemeAsync(value);
+        }
+    }
+
     private bool _autoTakeOwnership;
     public bool AutoTakeOwnership
     {
@@ -63,11 +77,12 @@ public partial class SettingsViewModel : FeatureViewModelBase
     public IAsyncRelayCommand BrowseMspLogoCommand { get; }
     public IAsyncRelayCommand ClearMspLogoCommand { get; }
 
-    public SettingsViewModel(SettingsService settingsService, IBrandingService brandingService, ILogger<FeatureViewModelBase> logger)
+    public SettingsViewModel(SettingsService settingsService, IBrandingService brandingService, ThemeManager themeManager, ILogger<FeatureViewModelBase> logger)
         : base(logger)
     {
         _settingsService = settingsService;
         _brandingService = brandingService;
+        _themeManager = themeManager;
         BrowseFolderCommand = new RelayCommand(BrowseFolder);
         BrowseMspLogoCommand = new AsyncRelayCommand(BrowseMspLogoAsync);
         ClearMspLogoCommand = new AsyncRelayCommand(ClearMspLogoAsync);
@@ -79,14 +94,29 @@ public partial class SettingsViewModel : FeatureViewModelBase
         _selectedLanguage = settings.Lang;
         _dataFolder = settings.DataFolder;
         _autoTakeOwnership = settings.AutoTakeOwnership;
+        _selectedTheme = settings.Theme;
         OnPropertyChanged(nameof(SelectedLanguage));
         OnPropertyChanged(nameof(DataFolder));
         OnPropertyChanged(nameof(AutoTakeOwnership));
+        OnPropertyChanged(nameof(SelectedTheme));
 
         var mspLogo = await _brandingService.GetMspLogoAsync();
         MspLogoPreview = mspLogo is not null ? $"data:{mspLogo.MimeType};base64,{mspLogo.Base64}" : null;
     }
 
+    private async Task ApplyThemeAsync(string mode)
+    {
+        try
+        {
+            _themeManager.ApplyFromString(mode);
+            await _settingsService.SetThemeAsync(mode);
+        }
+        catch (Exception ex)
+        {
+            StatusMessage = ex.Message;
+        }
+    }
+
     private async Task ApplyLanguageAsync(string code)
     {
         try