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

common/src/main/java/com/ecep/contract/model/DeliverySignMethod.java

@@ -4,6 +4,7 @@ import java.io.Serializable;
 import java.util.Objects;
 
 import com.ecep.contract.util.HibernateProxyUtils;
+import com.ecep.contract.vo.DeliverySignMethodVo;
 
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
@@ -25,7 +26,7 @@ import lombok.ToString;
 @Setter
 @Entity
 @Table(name = "PRODUCT_DELIVERY_SIGN_METHOD", schema = "supplier_ms")
-public class DeliverySignMethod implements BasedEntity, IdentityEntity , Serializable {
+public class DeliverySignMethod implements BasedEntity, IdentityEntity , Serializable, Voable<DeliverySignMethodVo> {
     private static final long serialVersionUID = 1L;
     @Id
     @Column(name = "ID", nullable = false)
@@ -68,4 +69,17 @@ public class DeliverySignMethod implements BasedEntity, IdentityEntity , Seriali
     public final int hashCode() {
         return HibernateProxyUtils.hashCode(this);
     }
+
+    @Override
+    public DeliverySignMethodVo toVo() {
+        DeliverySignMethodVo vo = new DeliverySignMethodVo();
+        vo.setId(id);
+        vo.setName(name);
+        vo.setCode(code);
+        vo.setSaleTypeId(saleType != null ? saleType.getId() : null);
+        vo.setDescription(description);
+        vo.setActive(false);
+        vo.setCreated(null);
+        return vo;
+    }
 }