feat(index): 首页随机姿势提示 + 移除冗余文案

- homeTip 从 config.postureTips 随机取一条，每次进首页换一条
- 移除圆环下方"平板支撑"单位文字，调整 ring 间距

pages/index/index.js

@@ -15,6 +15,7 @@ Page({
     todayDone: false,
     todayDuration: 0,
     todayTargetText: '',
+    homeTip: '',
     // Ring number font size in rpx. WeChat auto-scales text by the user's
     // font-size setting (fontSizeScaleFactor) but does NOT scale rpx box
     // dimensions — so on a real device with enlarged system font the 84rpx
@@ -147,6 +148,10 @@ Page({
     // 分段格子(每天一格)只在计划天数 <= 10 时用;更长则退化为里程碑连续条,避免格子过密
     const useSegments = plan.totalDays > 0 && plan.totalDays <= 10
     const planDays = useSegments ? Array.from({ length: plan.totalDays }, (_, i) => i) : []
+    // 首页姿势要领:从 config.postureTips 随机取一条,每次刷新都换,
+    // 让用户反复进首页能看到不同要领。配置为空时回退到默认文案,避免空白。
+    const tips = config.postureTips || []
+    const homeTip = tips.length ? tips[Math.floor(Math.random() * tips.length)] : '保持身体成一条直线，核心收紧，均匀呼吸'
     this.setData({
       theme,
       icons: iconsMod.build(theme),
@@ -160,7 +165,8 @@ Page({
       planTotal: plan.totalDays,
       planProgress,
       useSegments,
-      planDays
+      planDays,
+      homeTip
     })
   },