fix(dashboard): align leaderboard card heights by removing row-span-2

LiveSessionsPanel hardcoded rowSpan={2} which created an implicit
second grid row, making it 24px taller than adjacent leaderboard cards.

src/app/[locale]/dashboard/_components/bento/live-sessions-panel.tsx

@@ -165,7 +165,6 @@ export function LiveSessionsPanel({
     <BentoCard
       ref={containerRef}
       colSpan={1}
-      rowSpan={2}
       className={cn(
         "flex flex-col overflow-hidden p-0",
         // Light mode: subtle gray, Dark mode: terminal-style dark