修复：兼容Chrome公屏语音播放限制

问题：Chrome在页面没有用户操作时拒绝speechSynthesis并返回not-allowed，导致同机Safari有声但Chrome无声。
实现：两个公屏增加一次性声音启用操作，在用户手势中解锁语音；保留每次三遍播报，并补充暂停恢复、失败提示和回归测试。
复现：直接打开公屏页面后由员工端叫号，Chrome不播放声音。

web/src/hooks/useSpeechAnnouncements.ts

@@ -0,0 +1,63 @@
+import { useCallback, useState } from "react";
+
+export type SpeechAnnouncementStatus = "locked" | "enabling" | "ready" | "error" | "unsupported";
+
+const ANNOUNCEMENT_REPEAT_COUNT = 3;
+
+function speechSupported(): boolean {
+  return typeof window !== "undefined"
+    && "speechSynthesis" in window
+    && typeof SpeechSynthesisUtterance !== "undefined";
+}
+
+function createUtterance(text: string): SpeechSynthesisUtterance {
+  const utterance = new SpeechSynthesisUtterance(text);
+  utterance.lang = "zh-CN";
+  utterance.rate = 0.9;
+  return utterance;
+}
+
+export function useSpeechAnnouncements() {
+  const [status, setStatus] = useState<SpeechAnnouncementStatus>(() => (
+    speechSupported() ? "locked" : "unsupported"
+  ));
+
+  const enable = useCallback(() => {
+    if (!speechSupported()) {
+      setStatus("unsupported");
+      return;
+    }
+
+    const synthesis = window.speechSynthesis;
+    const utterance = createUtterance("叫号声音已开启。");
+    utterance.onstart = () => setStatus("ready");
+    utterance.onend = () => setStatus("ready");
+    utterance.onerror = (event) => {
+      if (event.error !== "canceled" && event.error !== "interrupted") setStatus("error");
+    };
+
+    setStatus("enabling");
+    synthesis.cancel();
+    if (synthesis.paused) synthesis.resume();
+    synthesis.speak(utterance);
+  }, []);
+
+  const announce = useCallback((announcements: string[]) => {
+    if (status !== "ready" || !announcements.length || !speechSupported()) return;
+
+    const synthesis = window.speechSynthesis;
+    synthesis.cancel();
+    if (synthesis.paused) synthesis.resume();
+    for (const announcement of announcements) {
+      for (let repeat = 0; repeat < ANNOUNCEMENT_REPEAT_COUNT; repeat += 1) {
+        const utterance = createUtterance(announcement);
+        utterance.onerror = (event) => {
+          if (event.error !== "canceled" && event.error !== "interrupted") setStatus("error");
+        };
+        synthesis.speak(utterance);
+      }
+    }
+  }, [status]);
+
+  return { announce, enable, status };
+}