feat: add TaskBoard demo and refactor project structure

.agent/AGENT_ARCHITECTURE_V2.md

@@ -163,6 +163,8 @@ graph BT
     ├── business/            # 💼 业务域
     │   ├── order-management/
     │   └── product-management/
+    ├── design/              # 🎨 设计规范
+    │   └── visual-standards/
     ├── tech-stack/          # 🛠️ 技术栈
     │   └── umijs-procomponents/
     └── engineering/         # 🛡️ 通用工程