feat: add change plan functionality to OrganizationSettings component

lib/api/billing.ts

@@ -64,6 +64,19 @@ export async function cancelSubscription(params?: CancelSubscriptionParams): Pro
   })
 }
 
+export interface ChangePlanParams {
+  plan_id: string
+  interval: string
+  limit: number
+}
+
+export async function changePlan(params: ChangePlanParams): Promise<{ ok: boolean }> {
+  return await billingFetch<{ ok: boolean }>('/api/billing/change-plan', {
+    method: 'POST',
+    body: JSON.stringify(params),
+  })
+}
+
 export interface CreateCheckoutParams {
   plan_id: string
   interval: string

lib/plans.ts

@@ -0,0 +1,29 @@
+/**
+ * Shared plan and traffic tier definitions for pricing and billing (Change plan).
+ * Backend supports plan_id "solo" and limit 10k–10M; month/year interval.
+ */
+
+export const PLAN_ID_SOLO = 'solo'
+
+/** Traffic tiers available for Solo plan (pageview limits). */
+export const TRAFFIC_TIERS = [
+  { label: '10k', value: 10000 },
+  { label: '50k', value: 50000 },
+  { label: '100k', value: 100000 },
+  { label: '250k', value: 250000 },
+  { label: '500k', value: 500000 },
+  { label: '1M', value: 1000000 },
+  { label: '2.5M', value: 2500000 },
+  { label: '5M', value: 5000000 },
+  { label: '10M', value: 10000000 },
+] as const
+
+export function getTierIndexForLimit(limit: number): number {
+  const idx = TRAFFIC_TIERS.findIndex((t) => t.value === limit)
+  return idx >= 0 ? idx : 2
+}
+
+export function getLimitForTierIndex(index: number): number {
+  if (index < 0 || index >= TRAFFIC_TIERS.length) return 100000
+  return TRAFFIC_TIERS[index].value
+}