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/Services/NotificationService.cs

@@ -0,0 +1,52 @@
+using CommunityToolkit.WinUI.Behaviors;
+using Ghost.Editor.Models;
+using Ghost.Editor.Services.Contracts;
+using Microsoft.UI.Xaml.Controls;
+using System;
+
+namespace Ghost.App.Services;
+
+public class NotificationService : INotificationService
+{
+    private InfoBar? _infoBar;
+    private StackedNotificationsBehavior? _notificationQueue;
+
+    internal void SetReference(InfoBar infoBar, StackedNotificationsBehavior notificationQueue)
+    {
+        _infoBar = infoBar;
+        _notificationQueue = notificationQueue;
+    }
+
+    public void ShowNotification(string? message, MessageType type, int duration = 5, string? title = null)
+    {
+        if (string.IsNullOrWhiteSpace(message))
+        {
+            return;
+        }
+
+        var notification = new Notification
+        {
+            Message = message,
+            Severity = (InfoBarSeverity)type,
+            Duration = TimeSpan.FromSeconds(duration),
+            Title = title
+        };
+
+        ShowNotification(notification);
+    }
+
+    public void ShowNotification(Notification notification)
+    {
+        _notificationQueue?.Show(notification);
+    }
+
+    internal void ClearReference()
+    {
+        if (_infoBar != null)
+        {
+            _infoBar.IsOpen = false;
+        }
+        _infoBar = null;
+        _notificationQueue = null;
+    }
+}