fix: 移除 @Slf4j 注解，改用显式 Logger 避免编译错误

cfc-backend/src/main/java/com/etotem/cfc/service/CouponService.java

@@ -19,7 +19,6 @@ import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-@Slf4j
 @Service
 public class CouponService {