feat(frontend): WebSocket 客户端 + Contact Store + API

- services/websocket.js: 单例 WS 连接管理（心跳/重连/事件分发）
- store/websocket.js: Pinia Store 管理连接状态
- store/contact.js: 联系人 Store（好友/申请/分组/黑名单/在线状态）
- api/contact.js: 联系人 REST API 封装（17 个接口）
- api/user.js: 用户搜索 API

Made-with: Cursor

frontend/src/api/contact.js

@@ -0,0 +1,116 @@
+/**
+ * 联系人模块 API
+ *
+ * 对应后端路由：/api/v1/contacts/*
+ * 接口文档见：docs/api/frontend/contact.md
+ */
+
+import { get, post, put, del } from '@/utils/request'
+
+/** 获取好友列表 */
+const getFriendList = (groupId) => {
+  const params = groupId ? { group_id: groupId } : {}
+  return get('/api/v1/contacts', params)
+}
+
+/** 发送好友申请 */
+const sendFriendRequest = (targetId, message = '') => {
+  return post('/api/v1/contacts/request', { target_id: targetId, message })
+}
+
+/** 接受好友申请 */
+const acceptRequest = (requestId) => {
+  return post('/api/v1/contacts/accept', { request_id: requestId })
+}
+
+/** 拒绝好友申请 */
+const rejectRequest = (requestId) => {
+  return post('/api/v1/contacts/reject', { request_id: requestId })
+}
+
+/** 获取待处理的好友申请 */
+const getPendingRequests = () => {
+  return get('/api/v1/contacts/requests')
+}
+
+/** 删除好友 */
+const deleteFriend = (friendId) => {
+  return del(`/api/v1/contacts/${friendId}`)
+}
+
+/** 更新好友备注 */
+const updateRemark = (friendId, remark) => {
+  return put(`/api/v1/contacts/${friendId}/remark`, { remark })
+}
+
+/** 拉黑用户 */
+const blockUser = (targetId) => {
+  return post('/api/v1/contacts/block', { target_id: targetId })
+}
+
+/** 取消拉黑 */
+const unblockUser = (userId) => {
+  return del(`/api/v1/contacts/block/${userId}`)
+}
+
+/** 获取黑名单 */
+const getBlockList = () => {
+  return get('/api/v1/contacts/block')
+}
+
+/** 获取分组列表 */
+const getGroups = () => {
+  return get('/api/v1/contacts/groups')
+}
+
+/** 创建分组 */
+const createGroup = (name) => {
+  return post('/api/v1/contacts/groups', { name })
+}
+
+/** 修改分组 */
+const updateGroup = (groupId, name, sortOrder) => {
+  const data = { name }
+  if (sortOrder !== undefined) data.sort_order = sortOrder
+  return put(`/api/v1/contacts/groups/${groupId}`, data)
+}
+
+/** 删除分组 */
+const deleteGroup = (groupId) => {
+  return del(`/api/v1/contacts/groups/${groupId}`)
+}
+
+/** 移动好友到分组 */
+const moveToGroup = (friendId, groupId) => {
+  return put(`/api/v1/contacts/${friendId}/group`, { group_id: groupId })
+}
+
+/** 搜索用户 */
+const searchUsers = (keyword, page = 1, pageSize = 20) => {
+  return get('/api/v1/users/search', { keyword, page, page_size: pageSize })
+}
+
+/** 好友推荐 */
+const getRecommendFriends = () => {
+  return get('/api/v1/contacts/recommend')
+}
+
+export default {
+  getFriendList,
+  sendFriendRequest,
+  acceptRequest,
+  rejectRequest,
+  getPendingRequests,
+  deleteFriend,
+  updateRemark,
+  blockUser,
+  unblockUser,
+  getBlockList,
+  getGroups,
+  createGroup,
+  updateGroup,
+  deleteGroup,
+  moveToGroup,
+  searchUsers,
+  getRecommendFriends
+}

frontend/src/api/user.js

@@ -0,0 +1,16 @@
+/**
+ * 用户搜索 API
+ *
+ * 对应后端路由：/api/v1/users/*
+ */
+
+import { get } from '@/utils/request'
+
+/** 搜索用户（按用户名/昵称模糊匹配） */
+const searchUsers = (keyword, page = 1, pageSize = 20) => {
+  return get('/api/v1/users/search', { keyword, page, page_size: pageSize })
+}
+
+export default {
+  searchUsers
+}