Adjust card width on desktop

The card width was too wide on desktop. Adjusted the width to be slightly smaller than the four icon area at the bottom.

src/components/BudgetCategoriesSection.tsx

@@ -14,7 +14,7 @@ const BudgetCategoriesSection: React.FC<BudgetCategoriesSectionProps> = ({ categ
   return (
     <>
       <h2 className="text-lg font-semibold mb-3 mt-8">지출 카테고리</h2>
-      <div className="grid gap-4 mb-8">
+      <div className="grid gap-4 mb-8 desktop-card">
         {categories.map((category, index) => (
           <BudgetCard 
             key={index}