fix: 修复 TypeScript 编译错误

修复以下问题：
- QuestionManagement.tsx: 修复 label 类型转换错误，使用 String() 确保类型安全
- UserDetail.tsx: 移除未使用的 Space 导入
- WrongQuestions.tsx: 显式声明 onChange 回调参数类型
- WrongQuestions.tsx: 使用空值合并运算符处理可能为 undefined 的值

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/pages/QuestionManagement.tsx

@@ -439,7 +439,7 @@ const QuestionManagement: React.FC = () => {
                       allowClear
                       showSearch
                       filterOption={(input, option) =>
-                        (option?.label ?? '').toLowerCase().includes(input.toLowerCase())
+                        String(option?.label ?? '').toLowerCase().includes(input.toLowerCase())
                       }
                     />
                   </Form.Item>

web/src/pages/UserDetail.tsx

@@ -4,7 +4,6 @@ import {
   Card,
   Button,
   Typography,
-  Space,
   message,
   Tag,
   Row,

web/src/pages/WrongQuestions.tsx

@@ -239,7 +239,7 @@ const WrongQuestions: React.FC = () => {
               placeholder="排序方式"
               style={{ width: 140 }}
               defaultValue="time"
-              onChange={(value) => setFilter({ ...filter, sort: value })}
+              onChange={(value: 'time' | 'wrong_count' | 'mastery_level') => setFilter({ ...filter, sort: value })}
             >
               <Option value="time">按时间排序</Option>
               <Option value="wrong_count">按错误次数</Option>
@@ -251,7 +251,7 @@ const WrongQuestions: React.FC = () => {
               type="primary"
               icon={<PlayCircleOutlined />}
               onClick={handlePractice}
-              disabled={!wrongQuestions.length || (stats?.total_wrong === stats?.mastered && stats?.total_wrong > 0)}
+              disabled={!wrongQuestions.length || (stats?.total_wrong === stats?.mastered && (stats?.total_wrong ?? 0) > 0)}
               className={styles.primaryButton}
             >
               开始练习