countdown: stop stretching rows to fill panel on large screens

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: zhgchgli0718

index.html

@@ -1158,6 +1158,7 @@
     display: grid;
     grid-template-columns: repeat(2, 1fr);
     gap: 12px 28px;
+    align-content: start;
   }
   .cd-item {
     display: grid;