简化侧边栏按钮边界检测逻辑

- 使用百分比计算边界，兼容所有设备
- 按钮活动范围：屏幕顶部10%到底部75%
- 移除复杂的safeArea判断，提高健壮性

pages/index/index.js

@@ -149,29 +149,16 @@ Page({
       let newTop = this.data.sidebarBtnTop + diffY * 2;
       
       const systemInfo = wx.getSystemInfoSync();
-      const screenHeight = systemInfo.screenHeight;
-      const safeArea = systemInfo.safeArea;
+      const screenHeight = systemInfo.screenHeight * 2;
       const btnHeight = 90;
-      const margin = 20;
-      const tabBarHeight = 70;
       
-      let minTop, maxTop;
+      const minTop = screenHeight * 0.1;
+      const maxTop = screenHeight * 0.75;
       
-      if (safeArea) {
-        minTop = safeArea.top + margin;
-        maxTop = safeArea.bottom - btnHeight - margin - tabBarHeight;
-      } else {
-        minTop = margin;
-        maxTop = screenHeight - btnHeight - margin - tabBarHeight;
-      }
-      
-      const minTopRpx = minTop * 2;
-      const maxTopRpx = maxTop * 2;
-      
-      if (newTop < minTopRpx) {
-        newTop = minTopRpx;
-      } else if (newTop > maxTopRpx) {
-        newTop = maxTopRpx;
+      if (newTop < minTop) {
+        newTop = minTop;
+      } else if (newTop > maxTop) {
+        newTop = maxTop;
       }
       
       this.setData({