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/app.ts

@@ -1,5 +1,5 @@
-import { UserProfile, GeoPoint, AppGlobalData } from './types/index'
-import { getCachedUser, login } from './utils/auth'
+import { AppGlobalData } from './types/index'
+import { getCachedUser } from './utils/auth'
 import { CLOUD_ENV, HEARTBEAT_INTERVAL_MS } from './utils/constants'
 import { api } from './utils/api'
 
@@ -44,16 +44,6 @@ App<{ globalData: AppGlobalData }>({
     this._stopLocationHeartbeat()
   },
 
-  async _initLogin() {
-    try {
-      const userInfo = await login()
-      this.globalData.userInfo = userInfo
-      this.globalData.isLoggedIn = true
-    } catch (e) {
-      console.error('Login failed', e)
-    }
-  },
-
   _initLocation() {
     wx.getLocation({
       type: 'gcj02',