chore: 清理冗余代码并补全私信/搜索/故事/通知功能

- 删除未使用的空组件目录、死代码导出(clearAuth/calcDistance/COLORS/
  AVATAR_GRADIENTS/Message/TabBarItem/deletePost/uploadImage/getFileURL/
  _initLogin)，确保程序仍可正常运行
- 新增 8 个云函数并补全对应页面逻辑：getMessages/sendMessage(私信聊天)、
  getHotTopics/searchPosts/searchUsers(搜索)、getStory(故事，复用 posts
  集合)、getNotifications/markAllRead(基于点赞评论聚合的通知系统)
- 在 cloudbaserc.json 中注册全部新云函数，并通过 --deployMode zip 完成部署

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

miniprogram/utils/auth.ts

@@ -1,7 +1,6 @@
 import { UserProfile } from '../types/index'
 import { api } from './api'
 
-const TOKEN_KEY = 'wangquan_token'
 const USER_KEY = 'wangquan_user'
 
 export async function login(): Promise<UserProfile> {
@@ -19,11 +18,6 @@ export function getCachedUser(): UserProfile | null {
   }
 }
 
-export function clearAuth(): void {
-  wx.removeStorageSync(TOKEN_KEY)
-  wx.removeStorageSync(USER_KEY)
-}
-
 export async function requireLocation(): Promise<{ latitude: number; longitude: number }> {
   return new Promise((resolve, reject) => {
     wx.getLocation({