fix(接口测试): 修复自定义请求 Query 参数重复解析问题

【【接口测试】github#32188，场景详情里，自定义请求，点击&取消url后面的引用环境，query参数会重复添加，场景是postman文件导入的】
https://www.tapd.cn/55049933/bugtrace/bugs/view/1155049933001044216

Signed-off-by: fit2-zhao <yong.zhao@fit2cloud.com>

api-test/frontend/src/business/automation/scenario/common/CustomizeReqInfo.vue

@@ -151,16 +151,20 @@ export default {
               let keyValues = param.split('=');
               if (keyValues) {
                 this.isUrl = true;
-                this.request.arguments.splice(
-                  0,
-                  0,
-                  new KeyValue({
-                    name: keyValues[0],
-                    required: false,
-                    value: keyValues[1],
-                    isEdit: false,
-                  })
-                );
+                // 检查参数是否已经存在
+                const existingParam = this.request.arguments.find((arg) => arg.name === keyValues[0]);
+                if (!existingParam) {
+                  this.request.arguments.splice(
+                    0,
+                    0,
+                    new KeyValue({
+                      name: keyValues[0],
+                      required: false,
+                      value: decodeURIComponent(keyValues[1] || ''), // 解码值
+                      isEdit: false,
+                    })
+                  );
+                }
               }
             }
           });