/** 金额展示（不依赖 Intl / toLocaleString，兼容微信小程序） */
export function formatMoney(amount: number | string): string {
  const n = typeof amount === 'number' ? amount : Number(amount);
  if (!Number.isFinite(n)) return '0.00';
  const fixed = n.toFixed(2);
  const [intPart, dec] = fixed.split('.');
  const withComma = intPart.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
  return `${withComma}.${dec}`;
}