refactor: 提取 useShare hook，统一分享和剪贴板逻辑

新增 useShare（Web Share API + clipboard fallback），
消除 QrInviteModal、BlindboxRoomPage、ShareCardModal 三处重复的分享代码。

src/components/QrInviteModal.tsx

@@ -7,7 +7,7 @@ import type { SceneType } from "@/types";
 import { getSceneConfig } from "@/lib/sceneConfig";
 import Modal from "@/components/Modal";
 import Button from "@/components/Button";
-import { useToast } from "@/hooks/useToast";
+import { useShare } from "@/hooks/useShare";
 
 interface QrInviteModalProps {
   open: boolean;
@@ -22,40 +22,22 @@ export default function QrInviteModal({
   roomId,
   scene = "eat",
 }: QrInviteModalProps) {
-  const toast = useToast();
+  const { share, copyToClipboard } = useShare();
   const sceneConfig = getSceneConfig(scene);
   const inviteUrl =
     typeof window !== "undefined"
       ? `${window.location.origin}/invite/${roomId}`
       : "";
 
-  const handleCopy = useCallback(async () => {
-    try {
-      await navigator.clipboard.writeText(inviteUrl);
-      toast.show("邀请链接已复制，快去发给朋友吧！");
-    } catch {
-      toast.show("复制失败，请手动复制链接");
-    }
-  }, [inviteUrl, toast]);
+  const handleCopy = useCallback(
+    () => copyToClipboard(inviteUrl, "邀请链接已复制，快去发给朋友吧！"),
+    [inviteUrl, copyToClipboard],
+  );
 
-  const handleShare = useCallback(async () => {
-    const shareData = {
-      title: sceneConfig.shareTitle,
-      text: sceneConfig.shareText,
-      url: inviteUrl,
-    };
-
-    try {
-      if (navigator.share && navigator.canShare?.(shareData)) {
-        await navigator.share(shareData);
-        return;
-      }
-    } catch (e) {
-      if (e instanceof Error && e.name === "AbortError") return;
-    }
-
-    handleCopy();
-  }, [inviteUrl, handleCopy, sceneConfig]);
+  const handleShare = useCallback(
+    () => share({ title: sceneConfig.shareTitle, text: sceneConfig.shareText, url: inviteUrl }, handleCopy),
+    [inviteUrl, sceneConfig, share, handleCopy],
+  );
 
   return (
     <Modal open={open} onClose={onClose}>