refactor: Toast 升级为全局 Context，消除 onToast prop 透传

将 useToast 从独立 state hook 改为 Context-based，在 layout 中
挂载 ToastProvider 全局渲染 Toast。QrInviteModal、RoomManageModal、
ShareCardModal 不再需要 onToast prop，直接 useToast() 调用即可。
父组件 TopNav、MatchResult、profile、blindbox 移除了本地 Toast
渲染和 onToast 传递逻辑。

src/components/QrInviteModal.tsx

@@ -6,12 +6,12 @@ import { X, Copy, Share2, QrCode } from "lucide-react";
 import type { SceneType } from "@/types";
 import { getSceneConfig } from "@/lib/sceneConfig";
 import Modal from "@/components/Modal";
+import { useToast } from "@/hooks/useToast";
 
 interface QrInviteModalProps {
   open: boolean;
   onClose: () => void;
   roomId: string;
-  onToast: (msg: string) => void;
   scene?: SceneType;
 }
 
@@ -19,9 +19,9 @@ export default function QrInviteModal({
   open,
   onClose,
   roomId,
-  onToast,
   scene = "eat",
 }: QrInviteModalProps) {
+  const toast = useToast();
   const sceneConfig = getSceneConfig(scene);
   const inviteUrl =
     typeof window !== "undefined"
@@ -31,11 +31,11 @@ export default function QrInviteModal({
   const handleCopy = useCallback(async () => {
     try {
       await navigator.clipboard.writeText(inviteUrl);
-      onToast("邀请链接已复制，快去发给朋友吧！");
+      toast.show("邀请链接已复制，快去发给朋友吧！");
     } catch {
-      onToast("复制失败，请手动复制链接");
+      toast.show("复制失败，请手动复制链接");
     }
-  }, [inviteUrl, onToast]);
+  }, [inviteUrl, toast]);
 
   const handleShare = useCallback(async () => {
     const shareData = {