Fix tetris UI spacing

Adjust Tetris layout to reduce empty space and align 2P preview with 1P, ensuring consistent game screen sizing across modes. Update container flex behavior to tighten layout and remove extra gap.

X-Lovable-Edit-ID: edt-28f420ea-db1f-429f-84e8-d26dac05573d

src/pages/Tetris.tsx

@@ -598,7 +598,7 @@ const Tetris = () => {
         </button>
       </div>
 
-      <div className={`flex ${isMobile ? 'flex-col items-center' : 'flex-row gap-4'} flex-1 ${isFullscreen ? 'justify-center items-center' : ''}`}>
+      <div className={`flex ${isMobile ? 'flex-col items-center' : 'flex-row gap-4'} flex-1 ${isFullscreen ? 'justify-center items-center' : 'justify-center items-start'}`}>
         {gameMode === '1p' ? (
           <>
             <div className="border-2 border-primary box-glow p-1 bg-background/80">{renderBoard1P()}</div>