feat: update voting timer styles (centered, grayscale, larger)

client/src/components/GameBoard.tsx

@@ -996,7 +996,7 @@ function VotingTimer() {
     }, [timeLeft]);
 
     return (
-        <div className="fixed top-5 left-5 bg-red-600/80 text-white w-16 h-16 rounded-full flex items-center justify-center border-4 border-red-400 animate-pulse text-2xl font-bold font-mono">
+        <div className="mx-auto my-2 bg-gray-900/90 text-white w-20 h-20 rounded-full flex items-center justify-center border-4 border-gray-500 text-3xl font-bold font-mono shadow-xl relative z-20">
             {timeLeft}
         </div>
     );