Web 端本地缓存、首页与会员弹窗体验优化

新增 IndexedDB 与最近文件 L1 缓存、云保存/打开链路；首页支持下载与清空本地缓存；修复清空 storage 后语言初始化报错；优化 design2 背景加载与侧栏标签样式；完善会员激活/支付弹层样式；后端补充文件缩略图字段与 thumb 接口。

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

frontend-web/js/common/member-pay-core.js

@@ -473,22 +473,29 @@
       displayChannels: channels,
     });
     var payCtrl = null;
+    var width = Math.min(480, window.innerWidth - 32);
     var idx = layer.open({
       type: 1,
       skin: 'soon-layer',
       title: false,
       closeBtn: 1,
+      fixed: true,
+      offset: 'auto',
+      shade: [0.72, '#000'],
       shadeClose: !!opts.shadeClose,
-      area: ['480px'],
+      maxWidth: width,
+      area: [width + 'px', 'auto'],
       content: html,
-      success: function (layero) {
+      success: function (layero, index) {
         var layerEl = layero && layero[0] ? layero[0] : layero;
         if (layerEl && layerEl.classList) {
           layerEl.classList.add('soon-layer--pay');
           var layerContent = layerEl.querySelector('.layui-layer-content');
           if (layerContent) {
+            layerContent.style.padding = '0';
             layerContent.style.overflow = 'visible';
             layerContent.style.maxHeight = 'none';
+            layerContent.style.background = 'transparent';
           }
         }
         var sheet = layerEl.querySelector('.soon-pay-sheet');
@@ -505,6 +512,9 @@
           },
           onBack: opts.onBack,
         });
+        requestAnimationFrame(function () {
+          if (typeof layer.style === 'function') layer.style(index);
+        });
       },
       end: function () {
         if (payCtrl) payCtrl.destroy();