Investigate default value for number inputs

The prompt asks to investigate the current default value (0) for number input fields and consider alternative approaches based on other applications.

src/components/expenses/ExpenseForm.tsx

@@ -59,7 +59,7 @@ const ExpenseForm: React.FC<ExpenseFormProps> = ({ onSubmit, onCancel }) => {
             <FormItem>
               <FormLabel>금액</FormLabel>
               <Input 
-                placeholder="0" 
+                placeholder="금액을 입력하세요" 
                 value={field.value}
                 onChange={handleAmountChange}
               />