fix: 修复快递100 OCR 签名调用和日志定义缺失

- hashlib.md5() 替代 hashlib.new()（hashlib 无 .new 方法）
- 补回被替换脚本丢失的 import logging 和 logger 定义

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/logistics_service.py

@@ -9,6 +9,7 @@
 
 from datetime import datetime
 import json
+import logging
 from urllib import error, request
 
 from sqlalchemy.exc import SQLAlchemyError
@@ -25,6 +26,8 @@ from backend.app.services.arrears_service import arrears_service
 from backend.app.services.audit_service import audit_service
 from backend.app.services.file_service import file_service
 
+logger = logging.getLogger(__name__)
+
 
 class LogisticsService:
     """物流服务，封装司机任务和物流轨迹的业务逻辑。
@@ -712,7 +715,7 @@ class LogisticsService:
 
                 # 3. 签名: MD5(param + key + customer) 转大写
                 sign_str = param_str + settings.kuaidi100_key + settings.kuaidi100_customer
-                sign = _md5.new(sign_str.encode("utf-8")).hexdigest().upper()
+                sign = _md5.md5(sign_str.encode("utf-8")).hexdigest().upper()
 
                 # 4. 构建 form-urlencoded 请求体
                 form_data = urlencode({