UI: remove the lobby game-row tap highlight

A tap/click on a lobby game row flashed a highlight on both tappable areas (the
open body and the right chevron/kebab), and the .open:active background lingered
while the finger was held — pointless feedback that only spoiled the look. Drop
the held :active background and set -webkit-tap-highlight-color: transparent on
the row's buttons.

ui/src/screens/Lobby.svelte

@@ -324,8 +324,13 @@
     user-select: none;
     touch-action: pan-y; /* keep vertical list scroll; we only read horizontal swipes */
   }
-  .open:active {
-    background: var(--surface-2);
+  /* A tap/click on a game row leaves no highlight: drop the WebKit tap-flash on
+     both tappable areas (the open body and the chevron / kebab) and the held
+     :active background, which added nothing and only spoiled the look. */
+  .open,
+  .chev,
+  .kebab {
+    -webkit-tap-highlight-color: transparent;
   }
   .kebab {
     flex: 0 0 auto;