docs: fix README.md project structure to match actual codebase

Engine modules:
- Audio: remove AudioSource/Listener components (they belong in Components/), add IAudioEffect.h
- Components: add AudioSourceComponent.h and AudioListenerComponent.h
- Math: remove non-existent OBB.h
- Resources: fix DependencyGraph.h -> ResourceDependencyGraph.h
- Threading: add TaskSystemConfig.h
- RHI: remove incorrect RHIDescriptor.h (already covered by RHIDescriptorPool.h)

Backend fixes:
- OpenGL: add OpenGLScreenshot.h
- D3D12: fix file order (D3D12Enum.h before D3D12Types.h)

docs/api/resources/texture-import-settings/setnormalmapstrength.md

@@ -0,0 +1,27 @@
+# TextureImportSettings::SetNormalMapStrength / GetNormalMapStrength
+
+```cpp
+void SetNormalMapStrength(float strength);
+float GetNormalMapStrength() const;
+```
+
+设置或获取法线贴图强度。
+
+**参数：**
+- `strength` - 法线贴图强度系数
+
+**返回：** `float` / `void`
+
+**线程安全：** ✅
+
+**示例：**
+
+```cpp
+TextureImportSettings settings;
+settings.SetNormalMapStrength(2.0f);
+float strength = settings.GetNormalMapStrength(); // 2.0f
+```
+
+## 相关文档
+
+- [TextureImportSettings 总览](textureimportsettings.md) - 返回类总览