task-4: extractErrorMessage 命名导出并覆盖 error/message/msg 三字段（空白跳过、优先级 error>message>msg）

frontend-vue/src/shared/api/http.ts

@@ -25,16 +25,18 @@ export interface JavaApiResponse<T> {
 }
 export type RequestOptions<D = unknown> = AxiosRequestConfig<D>
 
-function extractErrorMessage(error: unknown) {
+export function extractErrorMessage(error: unknown) {
   if (error instanceof AxiosError) {
     const data = error.response?.data
 
     if (data && typeof data === 'object') {
-      if ('error' in data && data.error) {
-        return String(data.error)
-      }
-      if ('message' in data && data.message) {
-        return String(data.message)
+      for (const field of ['error', 'message', 'msg'] as const) {
+        if (field in data && typeof (data as Record<string, unknown>)[field] === 'string') {
+          const value = ((data as Record<string, string>)[field]).trim()
+          if (value) {
+            return value
+          }
+        }
       }
     }