feat(04-03): implement FileTransferService with MoveCopyUtil and conflict policies

- FileTransferService.cs: CSOM copy/move via MoveCopyUtil.CopyFileByPath/MoveFileByPath
- Conflict policies: Skip (catch ServerException), Overwrite (overwrite=true), Rename (KeepBoth=true)
- ResourcePath.FromDecodedUrl for special character support
- Recursive folder enumeration with system folder filtering
- EnsureFolderAsync creates intermediate destination folders
- Best-effort metadata preservation (ResetAuthorAndCreatedOnCopy=false)
- FileTransferServiceTests.cs: 4 passing tests, 3 skipped (integration)

SharepointToolbox.Tests/Services/BulkMemberServiceTests.cs

@@ -0,0 +1,56 @@
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services;
+
+namespace SharepointToolbox.Tests.Services;
+
+public class BulkMemberServiceTests
+{
+    [Fact]
+    public void BulkMemberService_Implements_IBulkMemberService()
+    {
+        // GraphClientFactory requires MsalClientFactory which requires real MSAL setup
+        // Verify the type hierarchy at minimum
+        Assert.True(typeof(IBulkMemberService).IsAssignableFrom(typeof(BulkMemberService)));
+    }
+
+    [Fact]
+    public void BulkMemberRow_DefaultValues()
+    {
+        var row = new BulkMemberRow();
+        Assert.Equal(string.Empty, row.Email);
+        Assert.Equal(string.Empty, row.GroupName);
+        Assert.Equal(string.Empty, row.GroupUrl);
+        Assert.Equal(string.Empty, row.Role);
+    }
+
+    [Fact]
+    public void BulkMemberRow_PropertiesSettable()
+    {
+        var row = new BulkMemberRow
+        {
+            Email = "user@test.com",
+            GroupName = "Marketing",
+            GroupUrl = "https://contoso.sharepoint.com/sites/Marketing",
+            Role = "Owner"
+        };
+
+        Assert.Equal("user@test.com", row.Email);
+        Assert.Equal("Marketing", row.GroupName);
+        Assert.Equal("Owner", row.Role);
+    }
+
+    [Fact(Skip = "Requires live SharePoint tenant and Graph permissions")]
+    public async Task AddMembersAsync_ValidRows_AddsToGroups()
+    {
+    }
+
+    [Fact(Skip = "Requires live SharePoint tenant")]
+    public async Task AddMembersAsync_InvalidEmail_ReportsPerItemError()
+    {
+    }
+
+    [Fact(Skip = "Requires Graph permissions - Group.ReadWrite.All")]
+    public async Task AddMembersAsync_M365Group_UsesGraphApi()
+    {
+    }
+}