CREATE TABLE IF NOT EXISTS `users` (
  `id` INT AUTO_INCREMENT PRIMARY KEY,
  `username` VARCHAR(50) NOT NULL UNIQUE,
  `email` VARCHAR(100) NOT NULL UNIQUE,
  `password` VARCHAR(255) NOT NULL,
  `role` ENUM('user', 'admin') NOT NULL DEFAULT 'user',
  `balance` DECIMAL(10, 2) NOT NULL DEFAULT 0.00,
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);