fix(display): a hovered card no longer covers the top bar [CI SKIP]

web/display/src/display.css

@@ -2,7 +2,8 @@
 .topbar {
   position: sticky;
   top: 0;
-  z-index: 10;
+  /* 要比悬停中的卡片（z-index: 30，见下面）高：卡片滚到顶部栏下面时，鼠标悬停上去不能盖住顶部栏 */
+  z-index: 40;
   background: color-mix(in srgb, var(--app-bg), transparent 8%);
   backdrop-filter: blur(8px);
   border-bottom: 1px solid var(--app-outline-soft);