feat(ui): 迁移液态玻璃质感（TabBar/返回按钮）

- 自定义 TabBar 增加弯月面聚光带与银丝边缘，玻璃参数升级
- 全局返回按钮与 ScrollTopMask 返回按钮升级 135° 液态玻璃渐变
- 激活态升级为玻璃透镜，浅色/深色主题同步
- 新增 tools/liquid-glass.test.mjs 回归断言
- 同步构建产物 dist/，并合并此前未提交的 .claude 配置与 dist 变更

src/components/ScrollTopMask/index.scss

@@ -44,17 +44,37 @@
   justify-content: center;
   border-radius: 50%;
   pointer-events: auto;
-  background: rgba(255, 255, 255, 0.55);
-  backdrop-filter: blur(32px) saturate(1.2);
-  -webkit-backdrop-filter: blur(32px) saturate(1.2);
-  border: 1rpx solid rgba(255, 255, 255, 0.55);
-  box-shadow: 0 12rpx 40rpx rgba(0, 0, 0, 0.18), 0 4rpx 12rpx rgba(0, 0, 0, 0.08);
+  background: linear-gradient(
+    135deg,
+    rgba(255, 255, 255, 0.55) 0%,
+    rgba(255, 255, 255, 0.28) 45%,
+    rgba(255, 255, 255, 0.42) 100%
+  );
+  backdrop-filter: blur(24px) saturate(1.7) brightness(1.05);
+  -webkit-backdrop-filter: blur(24px) saturate(1.7) brightness(1.05);
+  border: 1rpx solid rgba(255, 255, 255, 0.35);
+  box-shadow:
+    inset 0 2rpx 3rpx rgba(255, 255, 255, 0.65),
+    inset 0 -2rpx 4rpx rgba(0, 0, 0, 0.06),
+    inset 0 0 0 1rpx rgba(255, 255, 255, 0.18),
+    0 12rpx 40rpx rgba(0, 0, 0, 0.18),
+    0 4rpx 12rpx rgba(0, 0, 0, 0.08);
 }
 
 .theme-dark .scroll-top-back {
-  background: rgba(25, 25, 25, 0.55);
-  border-color: rgba(255, 255, 255, 0.14);
-  box-shadow: 0 12rpx 40rpx rgba(0, 0, 0, 0.5), 0 4rpx 12rpx rgba(0, 0, 0, 0.3);
+  background: linear-gradient(
+    135deg,
+    rgba(255, 255, 255, 0.16) 0%,
+    rgba(255, 255, 255, 0.06) 45%,
+    rgba(255, 255, 255, 0.12) 100%
+  );
+  border-color: rgba(255, 255, 255, 0.18);
+  box-shadow:
+    inset 0 2rpx 3rpx rgba(255, 255, 255, 0.22),
+    inset 0 -2rpx 4rpx rgba(0, 0, 0, 0.28),
+    inset 0 0 0 1rpx rgba(255, 255, 255, 0.1),
+    0 12rpx 40rpx rgba(0, 0, 0, 0.5),
+    0 4rpx 12rpx rgba(0, 0, 0, 0.3);
 }
 
 .scroll-top-back-arrow {