feat(service): 实现国际化支持并优化Service层

重构文件类型相关Service以支持国际化查询
添加findOneByLang辅助方法统一查询逻辑
实现StringConverter支持UI控件显示
优化缓存配置和查询性能
新增UnitStringConverter和CustomerCatalogStringConverter
完善文档和测试用例

client/src/main/java/com/ecep/contract/task/ContractSyncTask.java

@@ -1,13 +1,12 @@
 package com.ecep.contract.task;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import com.ecep.contract.MessageHolder;
 import com.ecep.contract.SpringApp;
 import com.ecep.contract.WebSocketClientTasker;
-import com.ecep.contract.WebSocketClientService;
 import com.ecep.contract.service.YongYouU8Service;
-import com.fasterxml.jackson.core.JsonProcessingException;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 /**
  * 合同同步任务