feat(04-05): implement BulkSiteService with PnP Framework site creation

- BulkSiteService creates Team sites via TeamSiteCollectionCreationInformation with owners/members
- BulkSiteService creates Communication sites via CommunicationSiteCollectionCreationInformation with generated URL
- Per-site error handling via BulkOperationRunner with continue-on-error semantics
- SanitizeAlias generates URL-safe aliases from site names for Communication sites
- BulkSiteServiceTests: 3 pass (interface check + model defaults + CSV parsing), 3 skip (live SP)
- Fixed pre-existing BulkMemberService.cs Group type ambiguity (MSCSC.Group vs Graph.Models.Group)

SharepointToolbox.Tests/Services/BulkSiteServiceTests.cs

@@ -0,0 +1,56 @@
+using SharepointToolbox.Core.Models;
+using SharepointToolbox.Services;
+
+namespace SharepointToolbox.Tests.Services;
+
+public class BulkSiteServiceTests
+{
+    [Fact]
+    public void BulkSiteService_Implements_IBulkSiteService()
+    {
+        Assert.True(typeof(IBulkSiteService).IsAssignableFrom(typeof(BulkSiteService)));
+    }
+
+    [Fact]
+    public void BulkSiteRow_DefaultValues()
+    {
+        var row = new BulkSiteRow();
+        Assert.Equal(string.Empty, row.Name);
+        Assert.Equal(string.Empty, row.Alias);
+        Assert.Equal(string.Empty, row.Type);
+        Assert.Equal(string.Empty, row.Template);
+        Assert.Equal(string.Empty, row.Owners);
+        Assert.Equal(string.Empty, row.Members);
+    }
+
+    [Fact]
+    public void BulkSiteRow_ParsesCommaSeparatedEmails()
+    {
+        var row = new BulkSiteRow
+        {
+            Name = "Test Site",
+            Alias = "test-site",
+            Type = "Team",
+            Owners = "admin@test.com, user@test.com",
+            Members = "member1@test.com,member2@test.com"
+        };
+
+        Assert.Equal("Test Site", row.Name);
+        Assert.Contains("admin@test.com", row.Owners);
+    }
+
+    [Fact(Skip = "Requires live SharePoint admin context")]
+    public async Task CreateSitesAsync_TeamSite_CreatesWithOwners()
+    {
+    }
+
+    [Fact(Skip = "Requires live SharePoint admin context")]
+    public async Task CreateSitesAsync_CommunicationSite_CreatesWithUrl()
+    {
+    }
+
+    [Fact(Skip = "Requires live SharePoint admin context")]
+    public async Task CreateSitesAsync_MixedTypes_HandlesEachCorrectly()
+    {
+    }
+}