fix: 活动列表图片第二次上传静默失败（去limit并改为替换）

src/views/modules/activity/add.vue

@@ -72,7 +72,6 @@
                             ref="coverUploadRef"
                             :action="url"
                             :file-list="fileListCover"
-                            :limit="1"
                             :before-upload="file => beforeUploadHandle(file, 1, [158, 214], 'coverFile')"
                             list-type="picture-card"
                             :on-success="successHandleCover"
@@ -545,7 +544,12 @@ export default {
     initUploadSortable () {
       const setup = (ref, listKey, onChange) => {
         const listEl = this.$refs[ref] && this.$refs[ref].$el && this.$refs[ref].$el.querySelector('.el-upload-list--picture-card')
-        if (!listEl || listEl.__sortable) return
+        if (!listEl) return
+        // 如果之前绑定过，先销毁旧的，避免 element-ui 重渲染后引用陈旧
+        if (listEl.__sortable) {
+          listEl.__sortable.destroy()
+          listEl.__sortable = null
+        }
         listEl.__sortable = Sortable.create(listEl, {
           animation: 150,
           onEnd: (evt) => {
@@ -571,11 +575,9 @@ export default {
       if (res.code !== 0) {
         return this.$message.error(res.msg)
       }
-      this.fileListCover.unshift({
-        name: '',
-        url: res.data
-      })
-      this.basicForm.coverFile = this.fileListCover[0].url
+      // 活动列表图片只保留一张：直接替换而不是 unshift，避免与 el-upload 内部列表不一致导致第二次上传静默失败
+      this.fileListCover = [{ name: '', url: res.data }]
+      this.basicForm.coverFile = res.data
     },
     handleRemoveBanner (file, fileList) {
       this.fileListBanner = fileList.map((item) => item)