Add payment method selection

Adds a payment method selection (Credit Card, Cash) to the expense form and includes a line separator. Also requests to add a graph showing the proportion of credit card and cash usage in expense analytics, but this part is not implemented in this commit.

src/components/transaction/useTransactionEdit.ts

@@ -31,6 +31,7 @@ export const useTransactionEdit = (
       title: transaction.title,
       amount: formatWithCommas(transaction.amount.toString()),
       category: mapCategoryToNew(transaction.category),
+      paymentMethod: transaction.paymentMethod || '신용카드', // 지출 방법 추가, 기본값은 신용카드
     },
   });
   
@@ -41,6 +42,7 @@ export const useTransactionEdit = (
         title: transaction.title,
         amount: formatWithCommas(transaction.amount.toString()),
         category: mapCategoryToNew(transaction.category),
+        paymentMethod: transaction.paymentMethod || '신용카드', // 지출 방법 기본값
       });
     }
   }, [open, transaction, form]);
@@ -61,6 +63,7 @@ export const useTransactionEdit = (
         title: values.title,
         amount: Number(cleanAmount),
         category: values.category,
+        paymentMethod: values.paymentMethod, // 지출 방법 업데이트
       };
       
       // 컨텍스트를 통해 트랜잭션 업데이트