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/ShareCardModal.tsx

@@ -7,6 +7,7 @@ import { QRCodeSVG } from "qrcode.react";
 import { toPng } from "html-to-image";
 import type { Restaurant, MatchType, SceneType } from "@/types";
 import { useToast } from "@/hooks/useToast";
+import { useShare } from "@/hooks/useShare";
 
 type ShareCardData =
   | {
@@ -832,6 +833,8 @@ export default function ShareCardModal({
     toast.show("图片已保存");
   }, [handleGenerate, toast, data]);
 
+  const { share: nativeShare } = useShare();
+
   const handleShare = useCallback(async () => {
     const png = await handleGenerate();
     if (!png) {
@@ -840,20 +843,12 @@ export default function ShareCardModal({
     }
 
     const file = dataUrlToFile(png, "NoWhatever.png");
-
-    const shareData: ShareData = { files: [file] };
-    try {
-      if (navigator.canShare?.(shareData)) {
-        await navigator.share(shareData);
-        return;
-      }
-    } catch (e) {
-      if (e instanceof Error && e.name === "AbortError") return;
+    const shared = await nativeShare({ files: [file] });
+    if (!shared) {
+      downloadDataUrl(png, "NoWhatever.png");
+      toast.show("图片已保存，快去分享吧！");
     }
-
-    downloadDataUrl(png, "NoWhatever.png");
-    toast.show("图片已保存，快去分享吧！");
-  }, [handleGenerate, toast]);
+  }, [handleGenerate, toast, nativeShare]);
 
   const handleBackdropClick = (e: React.MouseEvent) => {
     if (e.target === backdropRef.current) onClose();