feat(player): 新增长页面一键回到顶部按钮

- 在 MainLayout 主滚动区挂载浮动回顶按钮，投注列表与赛事详情等长页通用

- 滚动超过阈值后显示，支持平滑回顶与底部导航避让

- 补充中/英/马来语文案 common.back_to_top

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/player/src/layouts/MainLayout.vue

@@ -9,6 +9,7 @@ import LocaleSwitcher from '../components/LocaleSwitcher.vue';
 import { useAppLocale } from '../composables/useAppLocale';
 import AnnouncementMarquee from '../components/AnnouncementMarquee.vue';
 import BottomNavIcon from '../components/BottomNavIcon.vue';
+import BackToTopButton from '../components/BackToTopButton.vue';
 import { computed, defineAsyncComponent, onMounted, ref, watch } from 'vue';
 
 const BetSlipDrawer = defineAsyncComponent(() => import('../components/BetSlipDrawer.vue'));
@@ -178,6 +179,8 @@ watch(
       </RouterLink>
     </nav>
 
+    <BackToTopButton :scroll-el="mainRef" :above-nav="showBottomNav" />
+
     <BetSlipDrawer v-model="slip.drawerOpen" />
     <CustomerServiceModal v-model="customerServiceOpen" />
   </div>