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/Controls/ViewModelPage.cs

@@ -1,38 +0,0 @@
-using CommunityToolkit.Mvvm.ComponentModel;
-using Ghost.Editor.Contracts;
-using Microsoft.UI.Xaml.Controls;
-using Microsoft.UI.Xaml.Navigation;
-
-namespace Ghost.Editor.Controls;
-
-public abstract partial class ViewModelPage<VM> : Page
-    where VM : ObservableObject
-{
-    public VM ViewModel
-    {
-        get;
-    }
-
-    protected ViewModelPage(VM viewModel)
-    {
-        ViewModel = viewModel;
-    }
-
-    protected override void OnNavigatedTo(NavigationEventArgs e)
-    {
-        base.OnNavigatedTo(e);
-        if (ViewModel is INavigationAware navigationAware)
-        {
-            navigationAware.OnNavigatedTo(e.Parameter);
-        }
-    }
-
-    protected override void OnNavigatedFrom(NavigationEventArgs e)
-    {
-        base.OnNavigatedFrom(e);
-        if (ViewModel is INavigationAware navigationAware)
-        {
-            navigationAware.OnNavigatedFrom();
-        }
-    }
-}