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/TestList/index.tsx

@@ -1,4 +1,4 @@
-import { PlayCircleOutlined, PlusOutlined } from '@ant-design/icons'
+import { EditOutlined, PlayCircleOutlined, PlusOutlined } from '@ant-design/icons'
 import { useQuery } from '@tanstack/react-query'
 import { Button, Space, Spin, Table, Tag, Typography } from 'antd'
 import type { ColumnsType } from 'antd/es/table'
@@ -64,6 +64,13 @@ export default function TestList() {
           <Button size="small" onClick={() => navigate(`/tests/${record.id}`)}>
             Открыть
           </Button>
+          <Button
+            size="small"
+            icon={<EditOutlined />}
+            onClick={() => navigate(`/tests/${record.id}/edit`)}
+          >
+            Изменить
+          </Button>
           <Button
             size="small"
             type="primary"