基本功能完成，下一步开始美化UI

.opencode/100-business/domain.yaml

@@ -20,6 +20,26 @@ domains:
           - name: "createdAt"
             type: "datetime"
             description: "创建时间"
+      - name: "UserGroup"
+        description: "用户组 (Note: The User Group feature (including management, assignment, and mixed selection) is implemented but currently UNTESTED. Missing Audit Log feature for User Group changes.)"
+        attributes:
+          - name: "id"
+            type: "string"
+            description: "用户组唯一标识"
+          - name: "name"
+            type: "string"
+            description: "用户组名称"
+          - name: "description"
+            type: "string"
+            description: "用户组描述"
+          - name: "isSystem"
+            type: "boolean"
+            description: "是否为系统内置组 (如: 全体用户)"
+          - name: "createdAt"
+            type: "datetime"
+            description: "创建时间"
+        rules:
+          - "All Users (全体用户) special group: Auto-join for new users; Cannot be deleted or modified; Users cannot exit."
 
   - name: "Question"
     description: "题库管理"
@@ -196,3 +216,18 @@ domains:
           - name: "updatedAt"
             type: "datetime"
             description: "更新时间"
+
+  - name: "Backup"
+    description: "数据备份与恢复"
+    entities:
+      - name: "BackupRestore"
+        description: "数据导出与导入"
+        attributes:
+          - name: "dataType"
+            type: "enum"
+            values: ["users", "questions", "records", "answers"]
+            description: "数据类型"
+          - name: "action"
+            type: "enum"
+            values: ["export", "restore"]
+            description: "操作类型"