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/components/SpeechControl.tsx

@@ -0,0 +1,38 @@
+import type { SpeechAnnouncementStatus } from "../hooks/useSpeechAnnouncements";
+
+interface SpeechControlProps {
+  status: SpeechAnnouncementStatus;
+  onEnable: () => void;
+}
+
+export function SpeechControl({ status, onEnable }: SpeechControlProps) {
+  if (status === "ready") {
+    return (
+      <aside className="speech-control speech-control--ready" role="status">
+        <strong>叫号声音已开启</strong>
+        <span>后续叫号将自动播报三次</span>
+      </aside>
+    );
+  }
+
+  const unsupported = status === "unsupported";
+  const failed = status === "error";
+  return (
+    <aside className={`speech-control${failed || unsupported ? " speech-control--error" : ""}`} role="status">
+      <div>
+        <strong>{unsupported ? "当前浏览器不支持叫号声音" : failed ? "叫号声音开启失败" : "叫号声音尚未开启"}</strong>
+        <span>{unsupported || failed ? "请确认系统已安装中文语音服务" : "Chrome 需要先点击一次，之后才允许自动播报"}</span>
+      </div>
+      {!unsupported ? (
+        <button
+          className="button button--primary"
+          type="button"
+          disabled={status === "enabling"}
+          onClick={onEnable}
+        >
+          {status === "enabling" ? "正在开启叫号声音" : failed ? "重新开启叫号声音" : "开启叫号声音"}
+        </button>
+      ) : null}
+    </aside>
+  );
+}