/* 返回按钮：从哪来回哪去（顶部 back-btn 与底部 back-link 共用同一逻辑） */
(function() {
var params = new URLSearchParams(window.location.search);
var referer = params.get('referer');
var target = referer
|| (document.referrer && document.referrer.indexOf(window.location.hostname) !== -1 ? document.referrer : 'index.html');
var backBtn = document.getElementById('backBtn');
if (backBtn) backBtn.href = target;
var backLink = document.getElementById('backLink');
if (backLink) backLink.href = target;
})();