Fix: Match chart colors to category list

Updated the expense chart to use the same colors as the category spending list for 음식, 쇼핑, and 교통비.

src/components/ExpenseChart.tsx

@@ -1,6 +1,7 @@
 
 import React from 'react';
 import { PieChart, Pie, Cell, ResponsiveContainer } from 'recharts';
+import { getCategoryColor } from '@/utils/categoryColorUtils';
 
 interface ExpenseData {
   name: string;