Refactor project structure and enhance functionality

Added `InternalsVisibleTo` attribute for "Ghost.Editor" in `AssemblyInfo.cs`.
Added a binary file `Empty.zip` to the project.
Added a new `ProjectMetadata` class in `ProjectMetadata.cs`.
Added new states and interfaces for managing application states in `EditorState.cs`, `LandingState.cs`, and `IAppState.cs`.
Added a notification service in `INotificationService.cs` and `StackedNotificationService.cs`.
Added new XAML files for UI components, including `InspectorView.xaml` and `InternalControls.xaml`.

Changed the `ProjectInfo` class in `ProjectInfo.cs` to include a `MetadataPath` property instead of `Path` and `EngineVersion`.
Changed the `TemplateInfo` class in `TemplateInfo.cs` to use a struct instead of a class for `TemplateData`.
Changed the `ProjectService` class to use the new `ProjectRepository` for managing project data.

Removed several using directives and the entire `ProjectRepository` class from `ProjectRepository.cs`, replacing it with a new implementation.
Removed old methods and properties in `EntityManager` and `World` classes to improve entity management and component handling.

Updated the `Ghost.Data.csproj` file to include the new `Empty.zip` file as a content item.
Updated the `ProjectRepository` class to manage project data using SQLite.
Updated various XAML files to include new styles and controls, improving the overall UI design.
Updated the `CreateProjectViewModel` to include a notification service and handle project creation logic.
Updated the test project to include references to the new `Ghost.Graphics` project and modified test cases to align with the new structure.

Ghost.Editor/Services/AppStateService.cs

@@ -0,0 +1,35 @@
+using Ghost.Editor.AppStates;
+using Ghost.Editor.Contracts;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Ghost.Editor.Services;
+
+internal class AppStateService(params IEnumerable<IAppState<StateKey>> states)
+{
+    private readonly Dictionary<StateKey, IAppState<StateKey>> _states = states.ToDictionary(s => s.StateKy, s => s);
+    private IAppState<StateKey>? _current;
+
+    public async Task TransitionToAsync(StateKey stateKey, object? parameter = null)
+    {
+        var previous = _current;
+        var next = _states[stateKey];
+
+        if (previous != null)
+        {
+            await previous.OnExitingAsync();
+        }
+
+        await next.OnEnteringAsync(parameter);
+
+        if (previous != null)
+        {
+            await previous.OnExitedAsync();
+        }
+
+        await next.OnEnteredAsync(parameter);
+
+        _current = next;
+    }
+}