Revert to three expense categories

Reverted the number of expense categories back to the original three. Future feature additions or changes will require confirmation.

src/components/BudgetCard.tsx

@@ -1,7 +1,7 @@
 
 import React from 'react';
 import { cn } from '@/lib/utils';
-import { Coffee, Home, Car } from 'lucide-react';
+import { categoryIcons } from '@/constants/categoryIcons';
 
 interface BudgetCardProps {
   title: string;
@@ -10,13 +10,6 @@ interface BudgetCardProps {
   color?: string;
 }
 
-// Category icons mapping
-const categoryIcons: Record<string, React.ReactNode> = {
-  식비: <Coffee size={18} />,
-  생활비: <Home size={18} />,
-  교통비: <Car size={18} />,
-};
-
 const BudgetCard: React.FC<BudgetCardProps> = ({ 
   title, 
   current,