refactor: 统一调用 showComingSoon & 防止重复触发

- coming-soon-mixin: 全局 \.info 配置 3s 自动关闭、顶部居中
- fwsc/xqsc: 禁用 tab 改走 showComingSoon
- qych: 卡片按钮使用 showComingSoon，外部链接固定 _blank 打开
- hyzt: 进入专题时加 messageShowing 锁，避免连点产生重复 toast

Co-authored-by: Cursor <cursoragent@cursor.com>

txw-mhzc-web/src/pages/index/utils/coming-soon-mixin.js

@@ -15,6 +15,11 @@ export default {
         prev.close()
         this[COMING_SOON_INSTANCE] = null
       }
+      this.$message.config({
+        duration: 3000, // 3s后自动关闭
+        placement: 'top', // 顶部居中
+        offset: [0, 100], // 离顶部100px
+      })
       this.$message.info(text).then((instance) => {
         this[COMING_SOON_INSTANCE] = instance
       })

txw-mhzc-web/src/pages/index/views/fwsc/xqsc.vue

@@ -424,7 +424,7 @@ export default {
     },
     goToTab({path, disable}) {
       if (disable) {
-        this.$message.info('敬请期待');
+        this.showComingSoon();
         return 
       }
       this.$router.push(path);

txw-mhzc-web/src/pages/index/views/hyzt/index.vue

@@ -39,6 +39,7 @@
 
 <script>
 import { mapState } from 'vuex';
+ 
 
 export default {
   name: 'hyzt',
@@ -55,11 +56,15 @@ export default {
       return index === 2 ? '进入交易大厅' : '进入专题';
     },
     goToHref(href) {
-      if (href) {
-        window.open(href, '_blank');
-      } else {
-        this.$message.info('敬请期待');
-      }
+      if (this.messageShowing) return;
+
+      this.messageShowing = true;
+
+      this.$message.info('敬请期待');
+
+      setTimeout(() => {
+        this.messageShowing = false;
+      }, 3000);
     },
   },
 };

txw-mhzc-web/src/pages/index/views/qych/index.vue

@@ -325,10 +325,10 @@ export default {
   methods: {
     goPage(url) {
       if (url) {
-        window.open(url);
-      } else {
-        this.$message.info('敬请期待')
+        window.open(url, '_blank');
+        return;
       }
+      this.showComingSoon();
     },
     handleCardBtnClick(item) {
       if (item.externalLink) {