feat(19-02): add app registration UI to profile dialog and 7 ViewModel tests

- ProfileManagementDialog.xaml: height 750, new Row 4 with Register/Remove buttons
- BooleanToVisibilityConverter added to Window.Resources
- Fallback instructions panel bound to ShowFallbackInstructions
- RegistrationStatus text block with StringToVisibilityConverter
- Buttons row shifted to Row 5
- ProfileManagementViewModelRegistrationTests: 7 unit tests, all passing
- ProfileManagementViewModelLogoTests: updated to 5-param constructor

SharepointToolbox.Tests/ViewModels/ProfileManagementViewModelLogoTests.cs

@@ -15,6 +15,7 @@ public class ProfileManagementViewModelLogoTests : IDisposable
 {
     private readonly string _tempFile;
     private readonly Mock<IBrandingService> _mockBranding;
+    private readonly Mock<IAppRegistrationService> _mockAppReg;
     private readonly GraphClientFactory _graphClientFactory;
     private readonly ILogger<ProfileManagementViewModel> _logger;
 
@@ -23,6 +24,7 @@ public class ProfileManagementViewModelLogoTests : IDisposable
         _tempFile = Path.GetTempFileName();
         File.Delete(_tempFile);
         _mockBranding = new Mock<IBrandingService>();
+        _mockAppReg = new Mock<IAppRegistrationService>();
         _graphClientFactory = new GraphClientFactory(new MsalClientFactory());
         _logger = NullLogger<ProfileManagementViewModel>.Instance;
     }
@@ -40,7 +42,8 @@ public class ProfileManagementViewModelLogoTests : IDisposable
             profileService,
             _mockBranding.Object,
             _graphClientFactory,
-            _logger);
+            _logger,
+            _mockAppReg.Object);
     }
 
     [Fact]
@@ -102,7 +105,8 @@ public class ProfileManagementViewModelLogoTests : IDisposable
             profileService,
             _mockBranding.Object,
             _graphClientFactory,
-            _logger);
+            _logger,
+            _mockAppReg.Object);
 
         vm.SelectedProfile = profile;
 
@@ -173,7 +177,8 @@ public class ProfileManagementViewModelLogoTests : IDisposable
             profileService,
             _mockBranding.Object,
             _graphClientFactory,
-            _logger);
+            _logger,
+            _mockAppReg.Object);
 
         vm.SelectedProfile = profile;
         Assert.NotNull(vm.ClientLogoPreview);