调整：叫号内容连续播报三次

需求：公屏每次播放叫号声音时重复三遍。
实现：单项目页和多项目公屏均为每个新批次排队三条相同语音，并更新回归测试。

web/src/pages/PublicDisplayCenterPage.tsx

@@ -37,10 +37,12 @@ export function PublicDisplayCenterPage() {
 
     window.speechSynthesis.cancel();
     for (const announcement of announcements) {
-      const utterance = new SpeechSynthesisUtterance(announcement);
-      utterance.lang = "zh-CN";
-      utterance.rate = 0.9;
-      window.speechSynthesis.speak(utterance);
+      for (let repeat = 0; repeat < 3; repeat += 1) {
+        const utterance = new SpeechSynthesisUtterance(announcement);
+        utterance.lang = "zh-CN";
+        utterance.rate = 0.9;
+        window.speechSynthesis.speak(utterance);
+      }
     }
   }, [data]);