fix: address board review and CI feedback

apps/nextjs/src/components/board/mobile/mobile-board.module.css

@@ -1,6 +1,6 @@
 .grid {
   display: grid;
-  grid-template-columns: repeat(2, minmax(0, 1fr));
+  grid-template-columns: repeat(var(--mobile-column-count), minmax(0, 1fr));
   grid-auto-flow: row;
   grid-auto-rows: min(calc((100vw - 42px) / 2), 12rem);
   gap: 10px;