抛弃轮询，使用websocket获取任务进度;部分优化;去除残留的条件判断;修复去除临时本子时加载不存在的预览图(同步更新)写死图片宽度;

src/components/DashBoard.vue

@@ -45,7 +45,7 @@
   <el-dialog title="查询本子" v-model="chosenGallery" style="height: 350px">
     <el-image v-show='chosenGallery.thumb_link !== undefined'
               style="float: right; width: 250px; height: 250px;" fit="contain"
-              :src="'https://downloader.lionwebsite.xyz/GalleryManage/ehThumbnail?path=' + chosenGallery.thumb_link"/>
+              :src="chosenGallery.thumb_link !== undefined ? 'https://downloader.lionwebsite.xyz/GalleryManage/ehThumbnail?path=' + chosenGallery.thumb_link: ''"/>
     <table>
       <tr>本子名字:{{chosenGallery.name}}</tr>
       <tr>本子页数:{{chosenGallery.pages}}</tr>
@@ -62,10 +62,9 @@
     </table>
     <template #footer>
       <el-button @click="postTask" v-if="chosenGallery.availableResolution">下载</el-button>
+      <el-button @click="window.open(chosenGallery.download)" v-else>下载文件</el-button>
       <el-button @click="readOnlineGallery(chosenGallery)">在线预览</el-button>
-      <tr v-if="chosenGallery.status === '下载完成'">
-        <el-button @click="deleteGallery">删除</el-button>
-      </tr>
+      <el-button v-if="chosenGallery.status === '下载完成'" @click="deleteGallery">删除</el-button>
     </template>
   </el-dialog>
 
@@ -111,7 +110,6 @@
       在线预览<hr>
       <span style="display: inline-block">在线预览分页页数:</span>
       <input v-model="lengthPerPage">
-      (建议为3的倍数，因为固定了一行三张)
     </div>
     <template #footer>
       <el-button type="primary" @click="saveConfig">保存</el-button>
@@ -157,6 +155,7 @@ let realAuthCode = computed(() => {
 
 let chosenGallery = computed(() => {
   param.value = ''
+  targetResolution.value = ''
   return store.state.chosenGallery
 })
 
@@ -203,7 +202,6 @@ function postTask(){
   store.dispatch("postGalleryTask",
       {link: chosenGallery.value.link,
               targetResolution: targetResolution.value})
-  targetResolution.value = ""
 }
 
 //查询任务