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/circle-detail/circle-detail.vue

@@ -1,5 +1,5 @@
 <template>
-  <view :class="themeClass" class="page-container detail-page">
+  <view class="page-container detail-page">
     <!-- 顶部导航 -->
     <view class="detail-nav" :style="{ paddingTop: navPaddingTop }">
       <view class="detail-nav-inner">
@@ -66,10 +66,8 @@ import FeedCard from '../../components/FeedCard.vue'
 import CommentItem from '../../components/CommentItem.vue'
 import EmptyState from '../../components/EmptyState.vue'
 import { GetFeedComments, AddComment, LikeFeed, UnlikeFeed, DeleteFeed, requireLogin } from '../../common/api'
-import themeMixin from '../../common/theme-mixin'
 
 export default {
-  mixins: [themeMixin],
   components: { FeedCard, CommentItem, EmptyState },
   data() {
     const menuBtn = uni.getMenuButtonBoundingClientRect()
@@ -98,17 +96,11 @@ export default {
       if (getCurrentPages().length > 1) {
         uni.navigateBack({
           fail: () => {
-            uni.switchTab({
-              url: '/pages/index/index',
-              fail: () => uni.reLaunch({ url: '/pages/index/index' })
-            })
+            uni.reLaunch({ url: '/pages/main/main?tab=0' })
           }
         })
       } else {
-        uni.switchTab({
-          url: '/pages/index/index',
-          fail: () => uni.reLaunch({ url: '/pages/index/index' })
-        })
+        uni.reLaunch({ url: '/pages/main/main?tab=0' })
       }
     },
     async loadFeed() {
@@ -219,7 +211,7 @@ export default {
     }
     return {
       title: '酒友圈 - 碰盏日记',
-      path: '/pages/index/index'
+      path: '/pages/main/main?tab=0'
     }
   }
 }