✨ feat: harden subscription billing and improve UI consistency

Improve subscription payment safety and data integrity by handling user/URL lookup failures, fixing Stripe subscription mode, persisting quota reset fields, and correcting subscription delta accounting and DB timestamp casting. Refine the UI with stricter custom duration validation, accurate currency rounding, conditional Epay labeling, rollback on preference update failure, and shared subscription formatting helpers plus clearer component naming.

web/src/helpers/subscriptionFormat.js

@@ -0,0 +1,34 @@
+export function formatSubscriptionDuration(plan, t) {
+  const unit = plan?.duration_unit || 'month';
+  const value = plan?.duration_value || 1;
+  const unitLabels = {
+    year: t('年'),
+    month: t('个月'),
+    day: t('天'),
+    hour: t('小时'),
+    custom: t('自定义'),
+  };
+  if (unit === 'custom') {
+    const seconds = plan?.custom_seconds || 0;
+    if (seconds >= 86400) return `${Math.floor(seconds / 86400)} ${t('天')}`;
+    if (seconds >= 3600) return `${Math.floor(seconds / 3600)} ${t('小时')}`;
+    return `${seconds} ${t('秒')}`;
+  }
+  return `${value} ${unitLabels[unit] || unit}`;
+}
+
+export function formatSubscriptionResetPeriod(plan, t) {
+  const period = plan?.quota_reset_period || 'never';
+  if (period === 'never') return t('不重置');
+  if (period === 'daily') return t('每天');
+  if (period === 'weekly') return t('每周');
+  if (period === 'monthly') return t('每月');
+  if (period === 'custom') {
+    const seconds = Number(plan?.quota_reset_custom_seconds || 0);
+    if (seconds >= 86400) return `${Math.floor(seconds / 86400)} ${t('天')}`;
+    if (seconds >= 3600) return `${Math.floor(seconds / 3600)} ${t('小时')}`;
+    if (seconds >= 60) return `${Math.floor(seconds / 60)} ${t('分钟')}`;
+    return `${seconds} ${t('秒')}`;
+  }
+  return t('不重置');
+}