feat(04-08): create TransferViewModel and TransferView

- TransferViewModel: source/dest site selection, transfer mode, conflict policy, confirmation dialog, per-item results, failed-items CSV export
- TransferView.xaml: DockPanel layout with GroupBoxes for source/dest, mode radio buttons, conflict policy ComboBox, progress bar, cancel button, export failed items button
- TransferView.xaml.cs: code-behind wires SitePickerDialog + FolderBrowserDialog for source and dest browsing
- Added EnumBoolConverter and StringToVisibilityConverter to IndentConverter.cs
- Registered converters in App.xaml; registered TransferViewModel, TransferView, IFileTransferService, BulkResultCsvExportService in App.xaml.cs

SharepointToolbox/App.xaml

@@ -8,6 +8,9 @@
         <conv:IndentConverter            x:Key="IndentConverter" />
         <conv:BytesConverter             x:Key="BytesConverter" />
         <conv:InverseBoolConverter       x:Key="InverseBoolConverter" />
+        <conv:EnumBoolConverter          x:Key="EnumBoolConverter" />
+        <conv:StringToVisibilityConverter x:Key="StringToVisibilityConverter" />
+        <conv:ListToStringConverter      x:Key="ListToStringConverter" />
         <Style x:Key="RightAlignStyle" TargetType="TextBlock">
             <Setter Property="HorizontalAlignment" Value="Right" />
         </Style>

SharepointToolbox/App.xaml.cs

@@ -119,6 +119,12 @@ public partial class App : Application
         services.AddTransient<Func<TenantProfile, SitePickerDialog>>(sp =>
             profile => new SitePickerDialog(sp.GetRequiredService<ISiteListService>(), profile));
 
+        // Phase 4: File Transfer
+        services.AddTransient<IFileTransferService, FileTransferService>();
+        services.AddTransient<BulkResultCsvExportService>();
+        services.AddTransient<TransferViewModel>();
+        services.AddTransient<TransferView>();
+
         services.AddSingleton<MainWindow>();
     }
 }

SharepointToolbox/ViewModels/Tabs/TransferViewModel.cs

@@ -0,0 +1,165 @@
+using System.Windows;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Microsoft.Extensions.Logging;
+using Microsoft.Win32;
+using Serilog;
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services;
+using SharepointToolbox.Services.Export;
+
+namespace SharepointToolbox.ViewModels.Tabs;
+
+public partial class TransferViewModel : FeatureViewModelBase
+{
+    private readonly IFileTransferService _transferService;
+    private readonly ISessionManager _sessionManager;
+    private readonly BulkResultCsvExportService _exportService;
+    private readonly ILogger<FeatureViewModelBase> _logger;
+    private TenantProfile? _currentProfile;
+
+    // Source selection
+    [ObservableProperty] private string _sourceSiteUrl = string.Empty;
+    [ObservableProperty] private string _sourceLibrary = string.Empty;
+    [ObservableProperty] private string _sourceFolderPath = string.Empty;
+
+    // Destination selection
+    [ObservableProperty] private string _destSiteUrl = string.Empty;
+    [ObservableProperty] private string _destLibrary = string.Empty;
+    [ObservableProperty] private string _destFolderPath = string.Empty;
+
+    // Transfer options
+    [ObservableProperty] private TransferMode _transferMode = TransferMode.Copy;
+    [ObservableProperty] private ConflictPolicy _conflictPolicy = ConflictPolicy.Skip;
+
+    // Results
+    [ObservableProperty] private string _resultSummary = string.Empty;
+    [ObservableProperty] private bool _hasFailures;
+
+    private BulkOperationSummary<string>? _lastResult;
+
+    public IAsyncRelayCommand ExportFailedCommand { get; }
+
+    // Expose current profile for View code-behind (site picker, folder browser)
+    public TenantProfile? CurrentProfile => _currentProfile;
+
+    // Dialog factories — set by View code-behind
+    public Func<string, bool>? ShowConfirmDialog { get; set; }
+
+    public TransferViewModel(
+        IFileTransferService transferService,
+        ISessionManager sessionManager,
+        BulkResultCsvExportService exportService,
+        ILogger<FeatureViewModelBase> logger)
+        : base(logger)
+    {
+        _transferService = transferService;
+        _sessionManager = sessionManager;
+        _exportService = exportService;
+        _logger = logger;
+
+        ExportFailedCommand = new AsyncRelayCommand(ExportFailedAsync, () => HasFailures);
+    }
+
+    protected override async Task RunOperationAsync(CancellationToken ct, IProgress<OperationProgress> progress)
+    {
+        if (_currentProfile == null)
+            throw new InvalidOperationException("No tenant connected.");
+
+        if (string.IsNullOrWhiteSpace(SourceSiteUrl) || string.IsNullOrWhiteSpace(SourceLibrary))
+            throw new InvalidOperationException("Source site and library must be selected.");
+
+        if (string.IsNullOrWhiteSpace(DestSiteUrl) || string.IsNullOrWhiteSpace(DestLibrary))
+            throw new InvalidOperationException("Destination site and library must be selected.");
+
+        // Confirmation dialog
+        var message = $"{TransferMode} files from {SourceLibrary} to {DestLibrary} ({ConflictPolicy} on conflict)";
+        if (ShowConfirmDialog != null && !ShowConfirmDialog(message))
+            return;
+
+        var job = new TransferJob
+        {
+            SourceSiteUrl = SourceSiteUrl,
+            SourceLibrary = SourceLibrary,
+            SourceFolderPath = SourceFolderPath,
+            DestinationSiteUrl = DestSiteUrl,
+            DestinationLibrary = DestLibrary,
+            DestinationFolderPath = DestFolderPath,
+            Mode = TransferMode,
+            ConflictPolicy = ConflictPolicy,
+        };
+
+        // Build per-site profiles so SessionManager can resolve contexts
+        var srcProfile = new TenantProfile
+        {
+            Name = _currentProfile.Name,
+            TenantUrl = SourceSiteUrl,
+            ClientId = _currentProfile.ClientId,
+        };
+        var dstProfile = new TenantProfile
+        {
+            Name = _currentProfile.Name,
+            TenantUrl = DestSiteUrl,
+            ClientId = _currentProfile.ClientId,
+        };
+
+        var srcCtx = await _sessionManager.GetOrCreateContextAsync(srcProfile, ct);
+        var dstCtx = await _sessionManager.GetOrCreateContextAsync(dstProfile, ct);
+
+        _lastResult = await _transferService.TransferAsync(srcCtx, dstCtx, job, progress, ct);
+
+        // Update UI on dispatcher
+        await Application.Current.Dispatcher.InvokeAsync(() =>
+        {
+            HasFailures = _lastResult.HasFailures;
+            ExportFailedCommand.NotifyCanExecuteChanged();
+
+            if (_lastResult.HasFailures)
+            {
+                ResultSummary = string.Format(
+                    Localization.TranslationSource.Instance["bulk.result.success"],
+                    _lastResult.SuccessCount, _lastResult.FailedCount);
+            }
+            else
+            {
+                ResultSummary = string.Format(
+                    Localization.TranslationSource.Instance["bulk.result.allsuccess"],
+                    _lastResult.TotalCount);
+            }
+        });
+    }
+
+    private async Task ExportFailedAsync()
+    {
+        if (_lastResult == null || !_lastResult.HasFailures) return;
+
+        var dlg = new SaveFileDialog
+        {
+            Filter = "CSV Files (*.csv)|*.csv",
+            FileName = "transfer_failed_items.csv",
+        };
+
+        if (dlg.ShowDialog() == true)
+        {
+            await _exportService.WriteFailedItemsCsvAsync(
+                _lastResult.FailedItems.ToList(),
+                dlg.FileName,
+                CancellationToken.None);
+            Log.Information("Exported failed transfer items to {Path}", dlg.FileName);
+        }
+    }
+
+    protected override void OnTenantSwitched(TenantProfile profile)
+    {
+        _currentProfile = profile;
+        SourceSiteUrl = string.Empty;
+        SourceLibrary = string.Empty;
+        SourceFolderPath = string.Empty;
+        DestSiteUrl = string.Empty;
+        DestLibrary = string.Empty;
+        DestFolderPath = string.Empty;
+        ResultSummary = string.Empty;
+        HasFailures = false;
+        _lastResult = null;
+    }
+}

SharepointToolbox/Views/Converters/IndentConverter.cs

@@ -45,3 +45,4 @@ public class InverseBoolConverter : IValueConverter
     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
         => value is bool b && !b;
 }
+

SharepointToolbox/Views/Tabs/TransferView.xaml

@@ -0,0 +1,81 @@
+<UserControl x:Class="SharepointToolbox.Views.Tabs.TransferView"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:loc="clr-namespace:SharepointToolbox.Localization">
+    <DockPanel Margin="10">
+        <!-- Options Panel (Left) -->
+        <StackPanel DockPanel.Dock="Left" Width="340" Margin="0,0,10,0">
+            <!-- Source -->
+            <GroupBox Header="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.sourcesite]}"
+                      Margin="0,0,0,10">
+                <StackPanel Margin="5">
+                    <TextBox Text="{Binding SourceSiteUrl, UpdateSourceTrigger=PropertyChanged}"
+                             IsReadOnly="True" Margin="0,0,0,5" />
+                    <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.browse]}"
+                            Click="BrowseSource_Click" Margin="0,0,0,5" />
+                    <TextBlock Text="{Binding SourceLibrary}" FontWeight="SemiBold" />
+                    <TextBlock Text="{Binding SourceFolderPath}" Foreground="Gray" />
+                </StackPanel>
+            </GroupBox>
+
+            <!-- Destination -->
+            <GroupBox Header="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.destsite]}"
+                      Margin="0,0,0,10">
+                <StackPanel Margin="5">
+                    <TextBox Text="{Binding DestSiteUrl, UpdateSourceTrigger=PropertyChanged}"
+                             IsReadOnly="True" Margin="0,0,0,5" />
+                    <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.browse]}"
+                            Click="BrowseDest_Click" Margin="0,0,0,5" />
+                    <TextBlock Text="{Binding DestLibrary}" FontWeight="SemiBold" />
+                    <TextBlock Text="{Binding DestFolderPath}" Foreground="Gray" />
+                </StackPanel>
+            </GroupBox>
+
+            <!-- Transfer Mode -->
+            <GroupBox Header="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.mode]}"
+                      Margin="0,0,0,10">
+                <StackPanel Margin="5">
+                    <RadioButton Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.mode.copy]}"
+                                 IsChecked="{Binding TransferMode, Converter={StaticResource EnumBoolConverter}, ConverterParameter=Copy}"
+                                 Margin="0,0,0,3" />
+                    <RadioButton Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.mode.move]}"
+                                 IsChecked="{Binding TransferMode, Converter={StaticResource EnumBoolConverter}, ConverterParameter=Move}" />
+                </StackPanel>
+            </GroupBox>
+
+            <!-- Conflict Policy -->
+            <GroupBox Header="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.conflict]}"
+                      Margin="0,0,0,10">
+                <ComboBox SelectedIndex="0" x:Name="ConflictCombo" SelectionChanged="ConflictCombo_SelectionChanged">
+                    <ComboBoxItem Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.conflict.skip]}" />
+                    <ComboBoxItem Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.conflict.overwrite]}" />
+                    <ComboBoxItem Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.conflict.rename]}" />
+                </ComboBox>
+            </GroupBox>
+
+            <!-- Actions -->
+            <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[transfer.start]}"
+                    Command="{Binding RunCommand}" Margin="0,0,0,5"
+                    IsEnabled="{Binding IsRunning, Converter={StaticResource InverseBoolConverter}}" />
+            <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[status.cancelled]}"
+                    Command="{Binding CancelCommand}"
+                    Visibility="{Binding IsRunning, Converter={StaticResource BoolToVisibilityConverter}}" />
+
+            <!-- Progress -->
+            <ProgressBar Height="20" Margin="0,10,0,5"
+                         Value="{Binding ProgressValue}"
+                         Visibility="{Binding IsRunning, Converter={StaticResource BoolToVisibilityConverter}}" />
+            <TextBlock Text="{Binding StatusMessage}" TextWrapping="Wrap" />
+
+            <!-- Results -->
+            <TextBlock Text="{Binding ResultSummary}" FontWeight="Bold" Margin="0,10,0,5"
+                       Visibility="{Binding ResultSummary, Converter={StaticResource StringToVisibilityConverter}}" />
+            <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[bulk.exportfailed]}"
+                    Command="{Binding ExportFailedCommand}"
+                    Visibility="{Binding HasFailures, Converter={StaticResource BoolToVisibilityConverter}}" />
+        </StackPanel>
+
+        <!-- Right panel placeholder for future enhancements -->
+        <Border />
+    </DockPanel>
+</UserControl>

SharepointToolbox/Views/Tabs/TransferView.xaml.cs

@@ -0,0 +1,99 @@
+using System.Windows;
+using System.Windows.Controls;
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services;
+using SharepointToolbox.Views.Dialogs;
+
+namespace SharepointToolbox.Views.Tabs;
+
+public partial class TransferView : UserControl
+{
+    private readonly ViewModels.Tabs.TransferViewModel _viewModel;
+    private readonly ISessionManager _sessionManager;
+    private readonly Func<TenantProfile, SitePickerDialog> _sitePickerFactory;
+
+    public TransferView(
+        ViewModels.Tabs.TransferViewModel viewModel,
+        ISessionManager sessionManager,
+        Func<TenantProfile, SitePickerDialog> sitePickerFactory)
+    {
+        InitializeComponent();
+        _viewModel = viewModel;
+        _sessionManager = sessionManager;
+        _sitePickerFactory = sitePickerFactory;
+        DataContext = viewModel;
+
+        viewModel.ShowConfirmDialog = message =>
+        {
+            var dlg = new ConfirmBulkOperationDialog(message) { Owner = Window.GetWindow(this) };
+            dlg.ShowDialog();
+            return dlg.IsConfirmed;
+        };
+    }
+
+    private async void BrowseSource_Click(object sender, RoutedEventArgs e)
+    {
+        if (_viewModel.CurrentProfile == null) return;
+
+        // Pick source site — SitePickerDialog returns a list; take the first selection for transfer
+        var sitePicker = _sitePickerFactory(_viewModel.CurrentProfile);
+        sitePicker.Owner = Window.GetWindow(this);
+        if (sitePicker.ShowDialog() != true) return;
+
+        var selectedSite = sitePicker.SelectedUrls.FirstOrDefault();
+        if (selectedSite == null) return;
+
+        _viewModel.SourceSiteUrl = selectedSite.Url;
+
+        // Browse library/folder for the selected source site
+        var profile = new TenantProfile
+        {
+            Name = _viewModel.CurrentProfile.Name,
+            TenantUrl = selectedSite.Url,
+            ClientId = _viewModel.CurrentProfile.ClientId,
+        };
+        var ctx = await _sessionManager.GetOrCreateContextAsync(profile, CancellationToken.None);
+        var folderBrowser = new FolderBrowserDialog(ctx) { Owner = Window.GetWindow(this) };
+        if (folderBrowser.ShowDialog() == true)
+        {
+            _viewModel.SourceLibrary = folderBrowser.SelectedLibrary;
+            _viewModel.SourceFolderPath = folderBrowser.SelectedFolderPath;
+        }
+    }
+
+    private async void BrowseDest_Click(object sender, RoutedEventArgs e)
+    {
+        if (_viewModel.CurrentProfile == null) return;
+
+        var sitePicker = _sitePickerFactory(_viewModel.CurrentProfile);
+        sitePicker.Owner = Window.GetWindow(this);
+        if (sitePicker.ShowDialog() != true) return;
+
+        var selectedSite = sitePicker.SelectedUrls.FirstOrDefault();
+        if (selectedSite == null) return;
+
+        _viewModel.DestSiteUrl = selectedSite.Url;
+
+        var profile = new TenantProfile
+        {
+            Name = _viewModel.CurrentProfile.Name,
+            TenantUrl = selectedSite.Url,
+            ClientId = _viewModel.CurrentProfile.ClientId,
+        };
+        var ctx = await _sessionManager.GetOrCreateContextAsync(profile, CancellationToken.None);
+        var folderBrowser = new FolderBrowserDialog(ctx) { Owner = Window.GetWindow(this) };
+        if (folderBrowser.ShowDialog() == true)
+        {
+            _viewModel.DestLibrary = folderBrowser.SelectedLibrary;
+            _viewModel.DestFolderPath = folderBrowser.SelectedFolderPath;
+        }
+    }
+
+    private void ConflictCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
+    {
+        if (ConflictCombo.SelectedIndex >= 0)
+        {
+            _viewModel.ConflictPolicy = (ConflictPolicy)ConflictCombo.SelectedIndex;
+        }
+    }
+}