feat: 实现基础设施层

axios 请求封装及七个业务模块 API，Pinia 状态管理（auth/system/models/tools），Mock 适配器与数据，以及流式对话、轮询、倒计时组合式函数。

frontend/src/api/request.ts

@@ -0,0 +1,73 @@
+import axios, { type AxiosInstance, type AxiosRequestConfig } from 'axios'
+import { ElMessage } from 'element-plus'
+
+/**
+ * 后端统一响应格式
+ * code === 0 表示成功，data 为业务数据
+ */
+export interface ApiResult<T = any> {
+  code: number
+  message?: string
+  data: T
+}
+
+const service: AxiosInstance = axios.create({
+  // 统一走相对路径，由 Vite 代理转发到 http://localhost:7861
+  baseURL: '/api',
+  timeout: 30000,
+})
+
+// 安装 mock adapter（拦截所有 axios 请求返回 mock 数据，方便前端独立开发调试）
+import { installMockAdapter } from '@/mock/adapter'
+installMockAdapter(service)
+
+// 请求拦截器
+service.interceptors.request.use(
+  (config) => config,
+  (error) => Promise.reject(error),
+)
+
+// 响应拦截器：统一解包 { code, data, message }
+service.interceptors.response.use(
+  (response) => {
+    const res = response.data as ApiResult
+    // 二进制流等非 JSON 响应直接返回
+    if (response.config.responseType === 'blob' || response.config.responseType === 'arraybuffer') {
+      return response
+    }
+    if (res.code === 0) {
+      return res.data
+    }
+    // 业务错误
+    const message = res.message || '请求失败'
+    ElMessage.error(message)
+    return Promise.reject(new Error(message))
+  },
+  (error) => {
+    const message = error.response?.data?.message || error.message || '网络异常'
+    ElMessage.error(message)
+    return Promise.reject(error)
+  },
+)
+
+/** GET 请求，返回已解包的 data */
+export function get<T = any>(url: string, params?: any, config?: AxiosRequestConfig): Promise<T> {
+  return service.get(url, { params, ...config }) as unknown as Promise<T>
+}
+
+/** POST 请求 */
+export function post<T = any>(url: string, data?: any, config?: AxiosRequestConfig): Promise<T> {
+  return service.post(url, data, config) as unknown as Promise<T>
+}
+
+/** PUT 请求 */
+export function put<T = any>(url: string, data?: any, config?: AxiosRequestConfig): Promise<T> {
+  return service.put(url, data, config) as unknown as Promise<T>
+}
+
+/** DELETE 请求 */
+export function del<T = any>(url: string, params?: any, config?: AxiosRequestConfig): Promise<T> {
+  return service.delete(url, { params, ...config }) as unknown as Promise<T>
+}
+
+export default service