feat: convert to nextjs

context/toast/ToastProvider.tsx

@@ -0,0 +1,23 @@
+import React, { useState, useCallback } from 'react';
+import { Toast, ToastContext } from './ToastContext';
+
+export const ToastProvider: React.FC<{ children: React.ReactNode }> = ({
+  children
+}) => {
+  const [toasts, setToasts] = useState<Toast[]>([]);
+
+  const showToast = useCallback((message: string) => {
+    const id = Date.now();
+    setToasts(prev => [...prev, { id, message }]);
+
+    setTimeout(() => {
+      setToasts(prev => prev.filter(toast => toast.id !== id));
+    }, 3000);
+  }, []);
+
+  return (
+    <ToastContext.Provider value={{ showToast, toasts }}>
+      {children}
+    </ToastContext.Provider>
+  );
+};