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/system/UserCreateView.vue

@@ -12,7 +12,7 @@ const form = reactive<CreateUserPayload>({
   username: '',
   display_name: '',
   password: 'platform123',
-  role: 'user',
+  role: 'operator',
   status: 'active',
   permissions: [],
 })
@@ -45,7 +45,7 @@ async function submit() {
       <el-form-item label="角色">
         <el-select v-model="form.role" style="width: 100%">
           <el-option label="管理员" value="admin" />
-          <el-option label="普通用户" value="user" />
+          <el-option label="普通用户" value="operator" />
         </el-select>
       </el-form-item>
       <el-form-item label="状态">