docs: Add Component, GameObject, TransformComponent and Scene API documentation

- Add Component class documentation with lifecycle methods
- Add GameObject class documentation with component system
- Add TransformComponent documentation with transform methods
- Add Scene class documentation with GameObject management
- Add SceneManager singleton documentation with scene loading
- Update components.md overview with all component classes
- Update main.md navigation with Scene module

docs/api/components/component/transform.md

@@ -0,0 +1,16 @@
+# Component::transform
+
+获取变换组件引用。
+
+```cpp
+TransformComponent& transform() const;
+```
+
+**返回：** `TransformComponent&` - 所属 GameObject 的变换组件引用
+
+**注意：** 如果组件未附加到 GameObject 或 GameObject 没有 TransformComponent，可能导致未定义行为。
+
+## 相关文档
+
+- [Component 总览](component.md)
+- [TransformComponent](transform-component/transform-component.md)