feat: split test detail into employee view and author view

- /tests/:id — employee view, answers shown without correct/incorrect markers
- /tests/:id/edit — author view, correct answers highlighted + edit button (disabled until Sprint 4)
- TestList: add 'Изменить' button linking to author view

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/TestDetail/index.tsx

@@ -1,4 +1,4 @@
-import { ArrowLeftOutlined, CheckCircleTwoTone, CloseCircleTwoTone, PlayCircleOutlined } from '@ant-design/icons'
+import { ArrowLeftOutlined, PlayCircleOutlined } from '@ant-design/icons'
 import { useQuery } from '@tanstack/react-query'
 import { Button, Card, Descriptions, List, Space, Spin, Tag, Typography } from 'antd'
 import { useNavigate, useParams } from 'react-router-dom'
@@ -78,14 +78,7 @@ export default function TestDetail() {
             dataSource={question.answers}
             renderItem={(answer: Answer) => (
               <List.Item style={{ padding: '4px 0' }}>
-                <Space>
-                  {answer.is_correct ? (
-                    <CheckCircleTwoTone twoToneColor="#52c41a" />
-                  ) : (
-                    <CloseCircleTwoTone twoToneColor="#d9d9d9" />
-                  )}
-                  <Text>{answer.text}</Text>
-                </Space>
+                <Text>{answer.text}</Text>
               </List.Item>
             )}
           />