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-children.md

@@ -0,0 +1,14 @@
+# GameObject::GetChildren
+
+获取所有子对象。
+
+```cpp
+std::vector<GameObject*> GetChildren() const;
+```
+
+**返回：** `std::vector<GameObject*>` - 包含所有子对象的向量
+
+## 相关文档
+
+- [GameObject 总览](game-object.md)
+- [GetChild](get-child.md)