fix(frontend): 修复操作日志与数据转换类型错误，修正普通用户角色取值

- OperationLogView: showDetail 调用补充 OperationLog 类型断言
- DataConvertView: beforeUpload 参数类型改为 UploadRawFile 并直接读取 file.type
- UserCreateView: 普通用户角色值 user 修正为 operator

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

frontend/src/views/data-convert/DataConvertView.vue

@@ -2,7 +2,7 @@
 import { onMounted, ref } from 'vue'
 import { ElMessage, ElMessageBox } from 'element-plus'
 import { Plus, Delete, Refresh } from '@element-plus/icons-vue'
-import type { TagProps, UploadRequestOptions, UploadFile } from 'element-plus'
+import type { TagProps, UploadRequestOptions, UploadFile, UploadRawFile } from 'element-plus'
 import PageCard from '@/components/PageCard.vue'
 import {
   getDataConvertTasks,
@@ -30,9 +30,9 @@ async function load() {
 }
 
 // 文件上传前的校验（仅校验文件格式）
-function beforeUpload(file: UploadFile) {
+function beforeUpload(file: UploadRawFile) {
   // 检查文件类型
-  const isJson = file.name.endsWith('.json') || file.raw?.type === 'application/json'
+  const isJson = file.name.endsWith('.json') || file.type === 'application/json'
   if (!isJson) {
     ElMessage.error('只能上传 .json 格式的文件')
     return false