添加iOS安全区域兼容

- 使用safeArea计算iPhone刘海边距
- 保留百分比作为安卓备用方案

pages/index/index.js

@@ -150,10 +150,18 @@ Page({
       
       const systemInfo = wx.getSystemInfoSync();
       const screenHeight = systemInfo.screenHeight * 2;
+      const safeArea = systemInfo.safeArea;
       const btnHeight = 90;
       
-      const minTop = screenHeight * 0.2;
+      let minTop, maxTop;
-      const maxTop = screenHeight * 0.75;
+      
+      if (safeArea && safeArea.top > 20) {
+        minTop = safeArea.top * 2 + 20;
+        maxTop = safeArea.bottom * 2 - btnHeight - 20;
+      } else {
+        minTop = screenHeight * 0.2;
+        maxTop = screenHeight * 0.6;
+      }
       
       if (newTop < minTop) {
         newTop = minTop;