feat(工单): 添加工单缺陷数量字段并优化导入逻辑

为工单模型添加缺陷数量字段，优化Excel导入逻辑
增加必填字段校验和异常处理，完善默认值设置

DOAN.Model/MES/Product/Dto/ProWorkorderDto.cs

@@ -58,8 +58,9 @@ namespace DOAN.Model.MES.product.Dto
 
         public string Unit { get; set; }
 
-        public int? PlanNum { get; set; }
-        public int? ShipmentNum { get; set; }
+        public int? PlanNum { get; set; } = 0;
+        public int? ShipmentNum { get; set; } = 0;
+        public int? DefectNum { get; set; } = 0;
         public int? Sort { get; set; }
 
         public DateTime? WorkorderDate { get; set; }