refactor(vo): 重构VO类及相关模型，添加Voable接口实现

feat(constant): 添加WebSocket错误码常量
docs(model): 为模型类添加注释
fix(service): 修复ProductUsageService缓存键问题
refactor(converter): 重构字符串转换器，移除EntityStringConverter依赖
feat(tab): 添加ComboBoxUtils工具类，优化下拉框初始化
style: 移除无用导入和字段

client/src/main/java/com/ecep/contract/converter/ContractGroupStringConverter.java

@@ -2,19 +2,17 @@ package com.ecep.contract.converter;
 
 import java.util.List;
 
+import com.ecep.contract.service.ContractGroupService;
+import javafx.util.StringConverter;
 import org.springframework.util.StringUtils;
 
 import com.ecep.contract.vo.ContractGroupVo;
 
-public class ContractGroupStringConverter extends EntityStringConverter<ContractGroupVo> {
+public class ContractGroupStringConverter extends StringConverter<ContractGroupVo> {
+    private ContractGroupService service;
 
-    private List<ContractGroupVo> dataset;
-
-    public ContractGroupStringConverter() {
-    }
-
-    public ContractGroupStringConverter(List<ContractGroupVo> dataset) {
-        this.dataset = dataset;
+    public ContractGroupStringConverter(ContractGroupService contractGroupService) {
+        this.service = contractGroupService;
     }
 
     @Override
@@ -22,32 +20,14 @@ public class ContractGroupStringConverter extends EntityStringConverter<Contract
         if (group == null) {
             return "All";
         }
-        return group.getName();
+        return group.getCode() + " " + group.getName() + " " + group.getTitle();
     }
 
     @Override
     public ContractGroupVo fromString(String string) {
-        if (dataset == null) {
-            return null;
-        }
         if (!StringUtils.hasText(string)) {
             return null;
         }
-
-        for (ContractGroupVo group : dataset) {
-            if (group == null) {
-                continue;
-            }
-            if (toString(group).equals(string)) {
-                return group;
-            }
-            if (group.getCode().equals(string)) {
-                return group;
-            }
-            if (group.getName().contains(string)) {
-                return group;
-            }
-        }
-        return null;
+        return service.findByCode(string);
     }
 }