Refactor project structure and enhance functionality

Changed the project namespace from `Ghost.Editor` to `Ghost.App` across multiple files.
Changed the `InternalsVisibleTo` attribute in `AssemblyInfo.cs` to include `Ghost.App`.
Changed the `ProjectRepository` class to add new asynchronous methods for retrieving projects by ID, name, and metadata path.
Changed the `ProjectService` class to utilize the new asynchronous project loading methods.
Changed the `SceneGraph` classes to improve node management and serialization.
Changed the `EntityManager` class to enhance entity management with new component handling methods.
Added new test classes, `EntityTest` and `SerializationTest`, to ensure reliability in entity and serialization systems.
Added the `Ghost.App` project file to establish a modular project structure.
Added the `Ghost.Generator` project for automated component serialization code generation.
Updated UI components to reflect the new namespace for proper functionality.

Ghost.Editor/View/Windows/LandingWindow.xaml.cs

@@ -1,61 +0,0 @@
-using Ghost.Data.Resources;
-using Ghost.Editor.Services;
-using Ghost.Editor.View.Pages.Landing;
-using Ghost.Engine.Resources;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.UI.Xaml.Controls;
-using Microsoft.UI.Xaml.Media.Animation;
-using WinUIEx;
-
-namespace Ghost.Editor.View.Windows;
-
-internal sealed partial class LandingWindow : WindowEx
-{
-    private IServiceScope? _landingScope;
-
-    private int _previousSelectedIndex;
-
-    public LandingWindow()
-    {
-        AppWindow.SetIcon(AssetsPath.s_appIconPath);
-        Title = EngineData.ENGINE_NAME;
-
-        InitializeComponent();
-
-        this.SetWindowSize(1000, 750);
-        this.CenterOnScreen();
-
-        ExtendsContentIntoTitleBar = true;
-    }
-
-    private void WindowEx_Activated(object sender, Microsoft.UI.Xaml.WindowActivatedEventArgs args)
-    {
-        _landingScope?.Dispose();
-        _landingScope = App.CreateScope();
-        App.GetService<StackedNotificationService>().SetReference(InfoBar, NotificationQueue);
-    }
-
-    private void WindowEx_Closed(object sender, Microsoft.UI.Xaml.WindowEventArgs args)
-    {
-        _landingScope?.Dispose();
-        App.GetService<StackedNotificationService>().ClearReference();
-    }
-
-    private void SelectorBar_SelectionChanged(SelectorBar sender, SelectorBarSelectionChangedEventArgs e)
-    {
-        var selectedItem = sender.SelectedItem;
-        var currentSelectedIndex = sender.Items.IndexOf(selectedItem);
-        var pageType = currentSelectedIndex switch
-        {
-            1 => typeof(CreateProjectPage),
-            _ => typeof(OpenProjectPage),
-        };
-
-        var slideNavigationTransitionEffect = currentSelectedIndex - _previousSelectedIndex > 0 ?
-            SlideNavigationTransitionEffect.FromRight : SlideNavigationTransitionEffect.FromLeft;
-
-        ContentFrame.Navigate(pageType, _landingScope, new SlideNavigationTransitionInfo() { Effect = slideNavigationTransitionEffect });
-
-        _previousSelectedIndex = currentSelectedIndex;
-    }
-}