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-activate.js

@@ -141,6 +141,8 @@
       }
       _gate.plan = plan;
       if (statusEl) statusEl.textContent = '';
+      var priceEl = modal.querySelector('.soon-activate-price__value');
+      if (priceEl) priceEl.textContent = '¥' + planPriceDisplay(plan);
       updatePayButton(modal);
     }).catch(function () {
       if (statusEl) statusEl.textContent = '网络错误，请稍后重试';
@@ -205,24 +207,36 @@
         try { layer.close(_gate.payIndex); } catch (e) { /* ignore */ }
       }
       _gate = { index: null, payIndex: null, plan: null, gateOpts: opts };
-      var width = Math.min(520, window.innerWidth - 24);
+      var width = Math.min(480, window.innerWidth - 32);
       layer.open({
         type: 1,
         skin: 'soon-layer',
         title: false,
         closeBtn: 1,
+        fixed: true,
+        offset: 'auto',
+        shade: [0.68, '#000'],
         shadeClose: true,
+        maxWidth: width,
         area: [width + 'px', 'auto'],
         content: shellHtml(opts.reason, null),
         success: function (layero, index) {
           var layerEl = layero && layero[0] ? layero[0] : layero;
-          if (layerEl && layerEl.classList) layerEl.classList.add('soon-layer--subscribe');
+          if (layerEl && layerEl.classList) {
+            layerEl.classList.add('soon-layer--activate');
+          }
           var content = layerEl && layerEl.querySelector ? layerEl.querySelector('.layui-layer-content') : null;
-          if (content) content.style.padding = '0';
+          if (content) {
+            content.style.padding = '0';
+            content.style.overflow = 'visible';
+          }
           var modal = layerEl.querySelector('.soon-activate-modal');
           _gate.index = index;
           _gate.gateOpts = opts;
           if (modal) bindModal(modal);
+          requestAnimationFrame(function () {
+            if (typeof layer.style === 'function') layer.style(index);
+          });
         },
         end: function () {
           var payIdx = _gate.payIndex;