Refactor budget storage utils

Splits the budget storage utils file into smaller, more manageable files for better organization and maintainability.

src/contexts/budget/useBudgetState.ts

@@ -1,4 +1,3 @@
-
 import { useCallback, useEffect } from 'react';
 import { BudgetPeriod } from './types';
 import { toast } from '@/components/ui/use-toast';
@@ -10,7 +9,7 @@ import {
   clearAllTransactions,
   clearAllCategoryBudgets,
   clearAllBudgetData
-} from './storageUtils';
+} from './storage';
 
 export const useBudgetState = () => {
   // 각 상태 관리 훅 사용