interface ReadingStats {
  userId: string;
  dailyReadingTime: number; // 单位:分钟
  dailyPages: number;
  monthlyStats: {
    month: string; // YYYY-MM
    totalTime: number;
    totalPages: number;
    finishedBooks: number;
  }[];
  yearlyGoal: {
    books: number;
    pages: number;
  };
}