feat(04-01): add Phase 4 models, interfaces, BulkOperationRunner, and test scaffolds

- Install CsvHelper 33.1.0 and Microsoft.Graph 5.74.0 (main + test projects)
- Add 14 core model/enum files (BulkOperationResult, BulkMemberRow, BulkSiteRow, TransferJob, FolderStructureRow, SiteTemplate, SiteTemplateOptions, TemplateLibraryInfo, TemplateFolderInfo, TemplatePermissionGroup, ConflictPolicy, TransferMode, CsvValidationRow)
- Add 6 service interfaces (IFileTransferService, IBulkMemberService, IBulkSiteService, ITemplateService, IFolderStructureService, ICsvValidationService)
- Add BulkOperationRunner with continue-on-error and cancellation support
- Add BulkResultCsvExportService stub (compile-ready)
- Add test scaffolds: BulkOperationRunnerTests (5 passing), BulkResultCsvExportServiceTests (2 passing), CsvValidationServiceTests (6 skipped), TemplateRepositoryTests (4 skipped)

SharepointToolbox.Tests/Services/BulkOperationRunnerTests.cs

@@ -0,0 +1,105 @@
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services;
+
+namespace SharepointToolbox.Tests.Services;
+
+public class BulkOperationRunnerTests
+{
+    [Fact]
+    public async Task RunAsync_AllSucceed_ReturnsAllSuccess()
+    {
+        var items = new List<string> { "a", "b", "c" };
+        var progress = new Progress<OperationProgress>();
+
+        var summary = await BulkOperationRunner.RunAsync(
+            items,
+            (item, idx, ct) => Task.CompletedTask,
+            progress,
+            CancellationToken.None);
+
+        Assert.Equal(3, summary.TotalCount);
+        Assert.Equal(3, summary.SuccessCount);
+        Assert.Equal(0, summary.FailedCount);
+        Assert.False(summary.HasFailures);
+    }
+
+    [Fact]
+    public async Task RunAsync_SomeItemsFail_ContinuesAndReportsPerItem()
+    {
+        var items = new List<string> { "ok1", "fail", "ok2" };
+        var progress = new Progress<OperationProgress>();
+
+        var summary = await BulkOperationRunner.RunAsync(
+            items,
+            (item, idx, ct) =>
+            {
+                if (item == "fail") throw new InvalidOperationException("Test error");
+                return Task.CompletedTask;
+            },
+            progress,
+            CancellationToken.None);
+
+        Assert.Equal(3, summary.TotalCount);
+        Assert.Equal(2, summary.SuccessCount);
+        Assert.Equal(1, summary.FailedCount);
+        Assert.True(summary.HasFailures);
+        Assert.Contains(summary.FailedItems, r => r.ErrorMessage == "Test error");
+    }
+
+    [Fact]
+    public async Task RunAsync_Cancelled_ThrowsOperationCanceled()
+    {
+        var items = new List<string> { "a", "b", "c" };
+        var cts = new CancellationTokenSource();
+        cts.Cancel();
+        var progress = new Progress<OperationProgress>();
+
+        await Assert.ThrowsAsync<OperationCanceledException>(() =>
+            BulkOperationRunner.RunAsync(
+                items,
+                (item, idx, ct) => Task.CompletedTask,
+                progress,
+                cts.Token));
+    }
+
+    [Fact]
+    public async Task RunAsync_CancelledMidOperation_StopsProcessing()
+    {
+        var items = new List<string> { "a", "b", "c", "d" };
+        var cts = new CancellationTokenSource();
+        var processedCount = 0;
+        var progress = new Progress<OperationProgress>();
+
+        await Assert.ThrowsAsync<OperationCanceledException>(() =>
+            BulkOperationRunner.RunAsync(
+                items,
+                async (item, idx, ct) =>
+                {
+                    Interlocked.Increment(ref processedCount);
+                    if (idx == 1) cts.Cancel(); // cancel after second item
+                    await Task.CompletedTask;
+                },
+                progress,
+                cts.Token));
+
+        Assert.True(processedCount <= 3); // should not process all 4
+    }
+
+    [Fact]
+    public async Task RunAsync_ReportsProgress()
+    {
+        var items = new List<string> { "a", "b" };
+        var progressReports = new List<OperationProgress>();
+        var progress = new Progress<OperationProgress>(p => progressReports.Add(p));
+
+        await BulkOperationRunner.RunAsync(
+            items,
+            (item, idx, ct) => Task.CompletedTask,
+            progress,
+            CancellationToken.None);
+
+        // Progress is async, give it a moment to flush
+        await Task.Delay(100);
+        Assert.True(progressReports.Count >= 2);
+    }
+}