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/RoomManageModal.tsx

@@ -13,6 +13,7 @@ import {
 import { UserProfile } from "@/types";
 import { getAvatar, getAvatarBg } from "@/lib/avatars";
 import Modal from "@/components/Modal";
+import { useToast } from "@/hooks/useToast";
 
 interface RoomManageModalProps {
   open: boolean;
@@ -24,7 +25,6 @@ interface RoomManageModalProps {
   swipeCounts: Record<string, number>;
   totalCards: number;
   userProfiles: Record<string, UserProfile>;
-  onToast: (msg: string) => void;
 }
 
 export default function RoomManageModal({
@@ -37,8 +37,8 @@ export default function RoomManageModal({
   swipeCounts,
   totalCards,
   userProfiles,
-  onToast,
 }: RoomManageModalProps) {
+  const toast = useToast();
   const [loading, setLoading] = useState<string | null>(null);
   const [confirmKick, setConfirmKick] = useState<string | null>(null);
   const [confirmEnd, setConfirmEnd] = useState(false);
@@ -54,33 +54,33 @@ export default function RoomManageModal({
         });
         if (!res.ok) {
           const data = await res.json().catch(() => ({}));
-          onToast(data.error ?? "操作失败");
+          toast.show(data.error ?? "操作失败");
           return;
         }
         switch (action) {
           case "lock":
-            onToast("房间已锁定，其他人无法加入");
+            toast.show("房间已锁定，其他人无法加入");
             break;
           case "unlock":
-            onToast("房间已解锁");
+            toast.show("房间已解锁");
             break;
           case "kick":
-            onToast("已将该用户移出房间");
+            toast.show("已将该用户移出房间");
             setConfirmKick(null);
             break;
           case "end_voting":
-            onToast("已结束投票，正在结算结果");
+            toast.show("已结束投票，正在结算结果");
             setConfirmEnd(false);
             onClose();
             break;
         }
       } catch {
-        onToast("操作失败，请重试");
+        toast.show("操作失败，请重试");
       } finally {
         setLoading(null);
       }
     },
-    [roomId, userId, onToast, onClose],
+    [roomId, userId, toast, onClose],
   );
 
   const otherUsers = users.filter((u) => u !== userId);