feat: add Graphics module with D3D12 backend and documentation

Graphics Module:
- Add platform abstraction layer (GraphicsPlatformInterface)
- Add unified renderer entry point (Renderer)
- Add D3D12 backend implementation (D3D12Core, D3D12Interface)
- Add TestRenderer for multi-window rendering tests

Documentation:
- Add Graphics渲染架构分析.md
- Add D3D12学习Wiki.md
- Add changelogs directory with per-commit documentation
- Add 20260326-dx12-initial.md for initial framework
- Add 20260326-d3d12-foundation.md for Graphics module

Fixes:
- Resolve header include issues and type redefinition errors

docs/changelogs/README.md

@@ -0,0 +1,24 @@
+# 变更日志索引
+
+本目录记录每次代码提交的详细变更文档。
+
+## 目录结构
+
+```
+changelogs/
+├── README.md           # 本文件 - 索引
+├── 2026-03/            # 按月份组织
+│   └── xxx.md          # 具体变更文档
+└── ...
+```
+
+## 变更记录
+
+| 日期 | 提交 | 变更内容 |
+|------|------|----------|
+| 2026-03-26 | [Graphics模块](./2026-03/20260326-d3d12-foundation.md) | Graphics 模块与 D3D12 后端框架 |
+| 2026-03-19 | [DX12初始框架](./2026-03/20260326-dx12-initial.md) | 初始 DX12 基础框架 |
+
+---
+
+> 每次提交变更后，请在对应月份目录下创建独立的变更文档。