Docs: Add audio module architecture design document

- Add XCEngine音频模块架构设计.md
- Design audio system following Unity-style architecture
- Include AudioSourceComponent, AudioListenerComponent, AudioClip, AudioMixer
- Document DSP effect system (FFT, Reverb, EQ, Compressor)
- Document 3D spatial audio with HRTF support
- Define IAudioBackend abstraction layer with WASAPI/OpenAL backends
- Outline 5-phase implementation priorities

engine/src/Scene/SceneManager.cpp

@@ -0,0 +1,116 @@
+#include "Scene/SceneManager.h"
+
+namespace XCEngine {
+namespace Components {
+
+SceneManager& SceneManager::Get() {
+    static SceneManager instance;
+    return instance;
+}
+
+Scene* SceneManager::CreateScene(const std::string& name) {
+    auto scene = std::make_unique<Scene>(name);
+    Scene* ptr = scene.get();
+    m_scenes[name] = std::move(scene);
+    
+    if (!m_activeScene) {
+        m_activeScene = ptr;
+    }
+    
+    m_onSceneLoaded.Invoke(ptr);
+    return ptr;
+}
+
+void SceneManager::LoadScene(const std::string& filePath) {
+    auto scene = std::make_unique<Scene>();
+    scene->Load(filePath);
+    Scene* ptr = scene.get();
+    
+    std::string name = filePath;
+    size_t pos = name.find_last_of("/\\");
+    if (pos != std::string::npos) {
+        name = name.substr(pos + 1);
+    }
+    pos = name.find_last_of('.');
+    if (pos != std::string::npos) {
+        name = name.substr(0, pos);
+    }
+    
+    m_scenes[name] = std::move(scene);
+    m_onSceneLoaded.Invoke(ptr);
+}
+
+void SceneManager::LoadSceneAsync(const std::string& filePath, std::function<void(Scene*)> callback) {
+    LoadScene(filePath);
+    if (callback) {
+        Scene* scene = GetScene(filePath);
+        callback(scene);
+    }
+}
+
+void SceneManager::UnloadScene(Scene* scene) {
+    if (!scene) {
+        return;
+    }
+    
+    if (m_activeScene == scene) {
+        m_activeScene = nullptr;
+    }
+    
+    auto it = m_scenes.begin();
+    while (it != m_scenes.end()) {
+        if (it->second.get() == scene) {
+            m_onSceneUnloaded.Invoke(scene);
+            it = m_scenes.erase(it);
+            break;
+        } else {
+            ++it;
+        }
+    }
+    
+    if (m_activeScene == nullptr && !m_scenes.empty()) {
+        m_activeScene = m_scenes.begin()->second.get();
+        m_onActiveSceneChanged.Invoke(m_activeScene);
+    }
+}
+
+void SceneManager::UnloadScene(const std::string& sceneName) {
+    auto it = m_scenes.find(sceneName);
+    if (it != m_scenes.end()) {
+        UnloadScene(it->second.get());
+    }
+}
+
+void SceneManager::SetActiveScene(Scene* scene) {
+    if (m_activeScene == scene) {
+        return;
+    }
+    m_activeScene = scene;
+    m_onActiveSceneChanged.Invoke(scene);
+}
+
+void SceneManager::SetActiveScene(const std::string& sceneName) {
+    auto it = m_scenes.find(sceneName);
+    if (it != m_scenes.end()) {
+        SetActiveScene(it->second.get());
+    }
+}
+
+Scene* SceneManager::GetScene(const std::string& name) const {
+    auto it = m_scenes.find(name);
+    if (it != m_scenes.end()) {
+        return it->second.get();
+    }
+    return nullptr;
+}
+
+std::vector<Scene*> SceneManager::GetAllScenes() const {
+    std::vector<Scene*> result;
+    for (auto& pair : m_scenes) {
+        result.push_back(pair.second.get());
+    }
+    return result;
+}
+
+} // namespace Components
+} // namespace XCEngine