refactor(editor): Complete architecture refactoring

- SceneManager: remove singleton, use dependency injection via EditorContext
- SelectionManager: already interface-based via ISelectionManager
- Panel: now receives IEditorContext for accessing managers
- HierarchyPanel: migrated to use IEditorContext instead of singletons
- Add ISceneManager interface and SceneManagerImpl
- EditorContextImpl: holds all editor subsystems

Architecture now follows dependency injection pattern:
Application -> EditorContext -> SceneManager/SelectionManager
EditorLayer -> Panels (receive context via SetContext)

All Manager singletons removed: EditorSceneManager::Get(), SelectionManager::Get()

editor/src/Managers/SceneManager.h

@@ -4,6 +4,8 @@
 #include <vector>
 #include <memory>
 #include <optional>
+#include <string>
+#include <cstdint>
 
 #include <XCEngine/Core/Event.h>
 #include <XCEngine/Core/Math/Vector3.h>
@@ -11,16 +13,17 @@
 #include <XCEngine/Components/GameObject.h>
 #include <XCEngine/Scene/Scene.h>
 
+#include "Core/ISelectionManager.h"
+
 namespace XCEngine {
 namespace Editor {
 
-class EditorSceneManager {
-public:
-    static EditorSceneManager& Get() {
-        static EditorSceneManager instance;
-        return instance;
-    }
+class ISelectionManager;
 
+class SceneManager {
+public:
+    SceneManager();
+    
     ::XCEngine::Components::GameObject* CreateEntity(const std::string& name, ::XCEngine::Components::GameObject* parent = nullptr);
 
     ::XCEngine::Components::GameObject* GetEntity(::XCEngine::Components::GameObject::ID id) {
@@ -37,12 +40,7 @@ public:
 
     void DeleteEntity(::XCEngine::Components::GameObject::ID id);
 
-    void RenameEntity(::XCEngine::Components::GameObject::ID id, const std::string& newName) {
-        if (auto* entity = GetEntity(id)) {
-            entity->SetName(newName);
-            OnEntityChanged.Invoke(id);
-        }
-    }
+    void RenameEntity(::XCEngine::Components::GameObject::ID id, const std::string& newName);
 
     void CopyEntity(::XCEngine::Components::GameObject::ID id);
     ::XCEngine::Components::GameObject::ID PasteEntity(::XCEngine::Components::GameObject::ID parent = 0);
@@ -52,6 +50,8 @@ public:
     void CreateDemoScene();
 
     bool HasClipboardData() const { return m_clipboard.has_value(); }
+    
+    void SetSelectionManager(ISelectionManager* selectionManager);
 
     ::XCEngine::Core::Event<::XCEngine::Components::GameObject::ID> OnEntityCreated;
     ::XCEngine::Core::Event<::XCEngine::Components::GameObject::ID> OnEntityDeleted;
@@ -59,8 +59,6 @@ public:
     ::XCEngine::Core::Event<> OnSceneChanged;
 
 private:
-    EditorSceneManager() = default;
-
     struct ClipboardData {
         std::string name;
         Math::Vector3 localPosition = Math::Vector3::Zero();
@@ -75,6 +73,7 @@ private:
     ::XCEngine::Components::Scene* m_scene = nullptr;
     std::vector<::XCEngine::Components::GameObject*> m_rootEntities;
     std::optional<ClipboardData> m_clipboard;
+    ISelectionManager* m_selectionManager = nullptr;
 };
 
 }