refactor(app): 重构应用主题和页面结构

- 移除动态主题切换功能，改为全局统一深色主题
- 实现自定义TabBar组件替换原生tabBar，解决iOS闪白问题
- 创建main容器页面统一管理三个tab页面的生命周期和状态
- 将所有页面的onShow/onHide等生命周期方法迁移到子组件内部
- 更新页面路径从index改为main，并调整路由跳转逻辑
- 移除theme-mixin和相关主题工具函数
- 统一页面背景色设置，优化用户体验一致性

pages/friends/friends.vue

@@ -1,5 +1,5 @@
 <template>
-  <view :class="themeClass" class="page-container friends-page">
+  <view class="page-container friends-page">
     <!-- 顶部导航 -->
     <view class="friends-nav" :style="{ paddingTop: navPaddingTop }">
       <view class="friends-nav-inner">
@@ -96,10 +96,8 @@ import FriendItem from '../../components/FriendItem.vue'
 import EmptyState from '../../components/EmptyState.vue'
 import { GetFriends, GetFriendRequests, AcceptFriendRequest, RemoveFriend } from '../../common/api'
 import { savePendingInvite, handlePendingInvite, getMyInviteCode } from '../../common/invite'
-import themeMixin from '../../common/theme-mixin'
 
 export default {
-  mixins: [themeMixin],
   components: { FriendItem, EmptyState },
   data() {
     const menuBtn = uni.getMenuButtonBoundingClientRect()
@@ -204,13 +202,13 @@ export default {
     const parts = []
     if (this.inviteCode) parts.push(`inviteCode=${encodeURIComponent(this.inviteCode)}`)
     if (user.nickname) parts.push(`inviterNick=${encodeURIComponent(user.nickname)}`)
-    const query = parts.length ? `?${parts.join('&')}` : ''
+    const query = parts.length ? `&${parts.join('&')}` : ''
     const nick = user.nickname ? `「${user.nickname}」` : ''
     // 本次分享已用掉当前邀请码，异步生成新码供下次分享
     this.refreshInviteCode()
     return {
       title: `${nick}邀请你成为酒友，一起记录饮酒生活 🍻`,
-      path: `/pages/index/index${query}`
+      path: `/pages/main/main?tab=0${query}`
     }
   }
 }