feat: implement descriptor heap with thread-safe allocation

D3D12 Resources:
- Add descriptor_handle struct with CPU/GPU handles
- Add descriptor_heap class for descriptor management
- Implement allocate() and free() methods
- Add mutex for thread-safe access
- Support all D3D12 descriptor heap types

D3D12 Core:
- Add device() function to expose main device
- Add release() template function for COM objects

Documentation:
- Add changelog for descriptor heap implementation
- Update D3D12 Wiki with descriptor heap section
- Mark descriptor heap task as completed

Engine/Graphics/Direct3D12/D3D12Core.h

@@ -1,4 +1,5 @@
 #pragma once
+#include "D3D12CommonHeader.h"
 
 /**
  * @brief Direct3D 12 核心类
@@ -22,6 +23,12 @@ void shutdown();
  */
 void render();
 
+
+/**
+ * @brief 通用资源释放模板函数
+ * @details 用于安全释放 DirectX COM 对象，检查空指针后调用 Release 并置空
+ * @tparam T COM 接口类型
+ */
 template<typename T>
 constexpr void release(T*& resource)
 {
@@ -32,4 +39,11 @@ constexpr void release(T*& resource)
     }
 }
 
+/**
+ * @brief 获取 Direct3D 12 设备
+ * @details 返回 Direct3D 12 设备的智能指针
+ * @return ID3D12Device* Direct3D 12 设备的智能指针
+ */
+ID3D12Device *const device();
+
 }// namespace XEngine::graphics::d3d12