底部导航选中项去掉背景胶囊，改为颜色+小圆点

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

mama-box.css

@@ -3249,3 +3249,8 @@ a.skip:focus{left:16px;top:16px}
 .exch-wrap{margin:16px -26px 0;padding:16px 26px 18px;border-radius:26px;position:relative;z-index:0;
   background-color:#fff;background-image:radial-gradient(170px 110px at 100% 0%, rgba(255,214,190,.38), rgba(255,214,190,0) 70%),linear-gradient(180deg,#FFFDFB,#FFF7F3)}
 .exch-wrap .exch-mod{margin-top:0}
+/* 2026-10-01 用户：选中项不要背景圆圈/底色，只靠颜色+加粗+图标弹一下 + 下方小圆点 */
+.tab::before{display:none}
+.tab::after{content:"";position:absolute;left:50%;bottom:6px;width:4px;height:4px;margin-left:-2px;border-radius:50%;background:#F4593C;opacity:0;transform:scale(0);transition:opacity .2s,transform .3s cubic-bezier(.3,1.6,.5,1)}
+.tab.is-active::after{opacity:1;transform:scale(1)}
+.tab-fab::after{display:none}