fix: 修复余额查询接口路径

添加 /strangeloop 前缀，修正 API 路径为 /strangeloop/api/credit/balance

src/services/creditsService.ts

@@ -94,7 +94,7 @@ export async function fetchBalance(): Promise<number | null> {
  * 调用 StrangeLoop 余额接口
  */
 async function callStrangeLoopBalance(token: string): Promise<StrangeLoopBalanceResponse> {
-  const urlStr = getStrangeLoopApiUrl('/api/credit/balance');
+  const urlStr = getStrangeLoopApiUrl('/strangeloop/api/credit/balance');
   const url = new URL(urlStr);
 
   const isHttps = url.protocol === 'https:';