feat: add data retention settings to SiteSettingsPage, including subscription-based options and UI updates for user interaction

lib/plans.ts

@@ -40,3 +40,42 @@ export function getLimitForTierIndex(index: number): number {
   if (index < 0 || index >= TRAFFIC_TIERS.length) return 100000
   return TRAFFIC_TIERS[index].value
 }
+
+/** Maximum data retention (months) allowed per plan. */
+export function getMaxRetentionMonthsForPlan(planId: string | null | undefined): number {
+  switch (planId) {
+    case 'business': return 60
+    case 'team': return 24
+    case 'solo': return 12
+    default: return 6
+  }
+}
+
+/** Selectable retention options (months) for the given plan. */
+export function getRetentionOptionsForPlan(planId: string | null | undefined): { label: string; value: number }[] {
+  const base = [
+    { label: '1 month', value: 1 },
+    { label: '3 months', value: 3 },
+    { label: '6 months', value: 6 },
+  ]
+  const solo = [...base, { label: '1 year', value: 12 }]
+  const team = [...solo, { label: '2 years', value: 24 }]
+  const business = [...team, { label: '3 years', value: 36 }, { label: '5 years', value: 60 }]
+
+  switch (planId) {
+    case 'business': return business
+    case 'team': return team
+    case 'solo': return solo
+    default: return base
+  }
+}
+
+/** Human-readable label for a retention value in months. */
+export function formatRetentionMonths(months: number): string {
+  if (months === 0) return 'Forever'
+  if (months === 1) return '1 month'
+  if (months < 12) return `${months} months`
+  const years = months / 12
+  if (Number.isInteger(years)) return years === 1 ? '1 year' : `${years} years`
+  return `${months} months`
+}