fix(player): 优化公告/消息详情页布局，隐藏右侧投注单

- 桌面端公告、消息详情页不再展示右侧投注单栏
- Hub 详情区移除重复返回按钮与竖排「查看全部公告」文字
- 左侧公告列表保留返回首页按钮

apps/player/src/views/MobileAnnouncementListView.vue

@@ -62,7 +62,14 @@ onActivated(() => {
 <template>
   <div class="announce-page" :class="{ 'is-embedded': embedded }">
     <header class="page-header">
-      <button type="button" class="back-btn" :aria-label="t('announcements.back')" @click="onBack">‹</button>
+      <button
+        type="button"
+        class="back-btn"
+        :aria-label="t('announcements.back')"
+        @click="onBack"
+      >
+        ‹
+      </button>
       <h1>{{ t('announcements.title') }}</h1>
     </header>