refactor(book_service): 优化下载文件方法中的变量命名

- 将变量名 file_res 统一更改为 response 提高代码可读性
- 保持原有的流式下载逻辑和错误处理机制不变
- 确保下载进度输出和文件写入功能正常工作

app/services/book_service.py

@@ -90,13 +90,13 @@ class BookService:
 
     @retry(stop=stop_after_attempt(3))
     def download_file(self, file_url, dir_name, file_name):  # 下载文件
-        file_res = self.session.get(file_url, stream=True)
+        response = self.session.get(file_url, stream=True)
-        file_res.raise_for_status()
+        response.raise_for_status()
-        print(f"下载状态码：{file_res.status_code} {file_url}")
+        print(f"下载状态码：{response.status_code} {file_url}")
         print(dir_name + "/" + file_name)
-        if self.isDownloadTarget(file_res):
+        if self.isDownloadTarget(response):
             with open(f"download/{self.setting["targetDate"]}/{dir_name}/{file_name}", 'wb') as file2:
-                for chunk in file_res.iter_content(chunk_size=1024):
+                for chunk in response.iter_content(chunk_size=1024):
                     if chunk:
                         file2.write(chunk)
             yield f"data: {self.setting["targetDate"]} {file_name}\n\n"