Refactor editor DI, update scene graph infra & deps

- Removed `[EditorInjectionAttribute]` and switched to direct service registration in `App.xaml.cs`
- Deleted `EditorIconSource` and moved icon handling to XAML
- Moved and enhanced `PathUtility` for path normalization and unique naming
- Renamed `SceneManager.UnloadScene` to `DestroyScene` for clarity
- Optimized `EntityQuery.Any()` with bitmask logic
- Improved `SceneGraphBuilder` and `SceneGraphSyncService` for better scene/entity handling
- Simplified entity field detection in `SceneSerializationService`
- Removed unused `TypeCache.Initialize()`
- Updated `ContentBrowser` to support scene asset creation and adjusted selection logic
- Upgraded NuGet package versions in project files
- Changed code generators to use `#if GHOST_EDITOR`
- Made `ShaderVariantCompiledHandler` safe
- Updated or removed scene graph planning docs to match new architecture

src/Editor/Ghost.Editor.Core/Attributes.cs

@@ -48,32 +48,6 @@ public class CustomEditorAttribute : DiscoverableAttributeBase
     }
 }
 
-[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = false, Inherited = false)]
-public class EditorInjectionAttribute : DiscoverableAttributeBase
-{
-    public enum ServiceLifetime
-    {
-        Singleton,
-        Transient,
-    }
-
-    public ServiceLifetime Lifetime
-    {
-        get;
-    }
-
-    public Type ImplementationType
-    {
-        get;
-    }
-
-    public EditorInjectionAttribute(ServiceLifetime lifetime, Type implementationType)
-    {
-        Lifetime = lifetime;
-        ImplementationType = implementationType;
-    }
-}
-
 [AttributeUsage(AttributeTargets.Method)]
 public sealed class ContextMenuItemAttribute : DiscoverableAttributeBase
 {