给采购和销售退货单增加校验逻辑，支持特殊情况的欠款，并给收付款单增加实际欠款的列

jshERP-web/src/views/bill/modules/PurchaseBackModal.vue

@@ -141,7 +141,7 @@
           </a-col>
           <a-col :lg="6" :md="12" :sm="24">
             <a-form-item :labelCol="labelCol" :wrapperCol="wrapperCol" label="本次退款">
-              <a-input placeholder="请输入本次退款" v-decorator.trim="[ 'changeAmount' ]" @keyup="onKeyUpChangeAmount" :readOnly="true"/>
+              <a-input placeholder="请输入本次退款" v-decorator.trim="[ 'changeAmount' ]" @keyup="onKeyUpChangeAmount" :readOnly="backStatus"/>
             </a-form-item>
           </a-col>
           <a-col :lg="6" :md="12" :sm="24">
@@ -214,6 +214,7 @@
         prefixNo: 'CGTH',
         fileList:[],
         rowCanEdit: true,
+        backStatus: true,
         model: {},
         labelCol: {
           xs: { span: 24 },
@@ -302,10 +303,14 @@
         if (this.action === 'add') {
           this.addInit(this.prefixNo)
           this.fileList = []
+          this.backStatus = true
         } else {
           if(this.model.linkNumber) {
             this.rowCanEdit = false
             this.materialTable.columns[1].type = FormTypes.normal
+            this.backStatus = false
+          } else {
+            this.backStatus = true
           }
           this.model.operTime = this.model.operTimeStr
           this.model.debt = (this.model.discountLastMoney + this.model.otherMoney - this.model.changeAmount).toFixed(2)
@@ -378,6 +383,7 @@
       },
       linkBillListOk(selectBillDetailRows, linkNumber, organId, discount, deposit, remark) {
         this.rowCanEdit = false
+        this.backStatus = false
         this.materialTable.columns[1].type = FormTypes.normal
         this.changeFormTypes(this.materialTable.columns, 'preNumber', 1)
         this.changeFormTypes(this.materialTable.columns, 'finishNumber', 1)