Refactor application structure and add unit tests

Added:
- New `ProgressService` class for managing progress indicators.
- New `AssetDatabase`, `AssetOpenHandlerAttribute`, and `AsyncAssetOpenHandlerAttribute` classes for asset handling.
- `Ghost.UnitTest` project for unit testing with associated files and configurations.

Changed:
- `ActivationHandler` class to ensure correct handling of `LaunchActivatedEventArgs`.
- `App.xaml.cs` to register `INotificationService` and `IProgressService`, replacing `StackedNotificationService`.
- `OnLaunched` method in `App.xaml.cs` to correctly call `ActivationHandler.Handle(args)` and start the host.
- `INavigationAware` interface from internal to public for broader access.
- `EditorState.cs` to activate `EditorApplication` with the current service provider.
- Property names in `AssetItem` and `ExplorerItem` structs to `Name` and `FullName`.
- `NotificationService` class to implement `INotificationService` and refactor notification handling.
- `AssetPathToGlyphConverter` to handle file extensions consistently.
- Bindings in `ProjectPage.xaml` and `ProjectPage.xaml.cs` to use `FullName` instead of `Path`.
- `EngineEditorWindow` and `LandingWindow` classes to utilize new notification and progress services.
- `Logger` class to include a new method for logging errors with exceptions.

Updated:
- Manifest files and project files to reflect new structure and dependencies.
- Solution file `GhostEngine.sln` to include the new unit test project.
- Added several new test classes and methods in `UnitTests.cs`.

Ghost.App/View/Pages/Landing/OpenProjectPage.xaml.cs

@@ -0,0 +1,71 @@
+using Ghost.Data.Models;
+using Ghost.Editor.ViewModels.Pages.Landing;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Navigation;
+using Windows.ApplicationModel.DataTransfer;
+
+namespace Ghost.App.View.Pages.Landing;
+
+internal sealed partial class OpenProjectPage : Page
+{
+    public OpenProjectViewModel ViewModel
+    {
+        get;
+    }
+
+    public OpenProjectPage()
+    {
+        ViewModel = GhostApplication.GetService<OpenProjectViewModel>();
+        InitializeComponent();
+    }
+
+    protected override void OnNavigatedTo(NavigationEventArgs e)
+    {
+        base.OnNavigatedTo(e);
+        ViewModel.OnNavigatedTo(e.Parameter);
+    }
+
+    override protected void OnNavigatedFrom(NavigationEventArgs e)
+    {
+        base.OnNavigatedFrom(e);
+        ViewModel.OnNavigatedFrom();
+    }
+
+    private void ProjectContainer_DragEnter(object sender, DragEventArgs e)
+    {
+        ViewModel.DragVisibility = Visibility.Visible;
+        ViewModel.EmptyVisibility = Visibility.Collapsed;
+    }
+
+    private void ProjectContainer_DragLeave(object sender, DragEventArgs e)
+    {
+        ViewModel.DragVisibility = Visibility.Collapsed;
+        ViewModel.UpdateEmptyPlaceHolderVisibility();
+    }
+
+    private void ProjectContainer_DragOver(object sender, DragEventArgs e)
+    {
+        if (e.DataView.Contains(StandardDataFormats.StorageItems))
+        {
+            e.AcceptedOperation = DataPackageOperation.Link;
+        }
+        else
+        {
+            e.AcceptedOperation = DataPackageOperation.None;
+        }
+    }
+
+    private async void ProjectContainer_Drop(object sender, DragEventArgs e)
+    {
+        await ViewModel.ContentDrop(e.DataView);
+    }
+
+    private async void ListView_ItemClick(object sender, ItemClickEventArgs e)
+    {
+        if (e.ClickedItem is ProjectMetadataInfo project)
+        {
+            await ViewModel.LoadProject(project);
+        }
+    }
+}