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/pages/search/search.ts

@@ -1,3 +1,4 @@
+import { api } from '../../utils/api'
 import { getAvatarGradient } from '../../utils/format'
 
 Page({
@@ -19,8 +20,8 @@ Page({
 
   async loadHotTopics() {
     try {
-      const res = await wx.cloud.callFunction({ name: 'getHotTopics', data: {} }) as any
-      this.setData({ hotTopics: res.result?.data || [] })
+      const topics = await api.getHotTopics()
+      this.setData({ hotTopics: topics || [] })
     } catch {}
   },
 
@@ -38,12 +39,12 @@ Page({
     this.setData({ loading: true })
     try {
       const [posts, users] = await Promise.all([
-        wx.cloud.callFunction({ name: 'searchPosts', data: { keyword: kw } }) as any,
-        wx.cloud.callFunction({ name: 'searchUsers', data: { keyword: kw } }) as any,
+        api.searchPosts(kw),
+        api.searchUsers(kw),
       ])
       this.setData({
-        postResults: posts.result?.data || [],
-        userResults: (users.result?.data || []).map((u: any) => ({
+        postResults: posts || [],
+        userResults: (users || []).map((u: any) => ({
           ...u,
           gradient: getAvatarGradient(u._id),
         })),