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/game-object/get-component.md

@@ -0,0 +1,23 @@
+# GameObject::GetComponent
+
+获取游戏对象上指定类型的组件。
+
+```cpp
+template<typename T>
+T* GetComponent();
+
+template<typename T>
+const T* GetComponent() const;
+```
+
+使用 dynamic_cast 在组件列表中查找匹配类型的第一个组件。
+
+**模板参数：**
+- `T` - 组件类型
+
+**返回：** `T*` - 找到的组件指针，如果未找到则返回 nullptr
+
+## 相关文档
+
+- [GameObject 总览](game-object.md)
+- [GetComponents](get-components.md)