feat(payment): confirm renewal only at checkout

src/lib/payment/automatic_renewal_acknowledgement.ts

@@ -0,0 +1,33 @@
+export const AUTOMATIC_RENEWAL_AGREEMENT_VERSION = "2026-07-29";
+
+const STORAGE_PREFIX = "cozsweet.automatic-renewal-acknowledged";
+
+function storageKey(subjectId: string | null | undefined): string | null {
+  const normalized = subjectId?.trim();
+  if (!normalized) return null;
+  return `${STORAGE_PREFIX}:${AUTOMATIC_RENEWAL_AGREEMENT_VERSION}:${encodeURIComponent(normalized)}`;
+}
+
+export function hasAutomaticRenewalAcknowledgement(
+  subjectId: string | null | undefined,
+): boolean {
+  const key = storageKey(subjectId);
+  if (!key || typeof window === "undefined") return false;
+  try {
+    return window.localStorage.getItem(key) === "confirmed";
+  } catch {
+    return false;
+  }
+}
+
+export function rememberAutomaticRenewalAcknowledgement(
+  subjectId: string | null | undefined,
+): void {
+  const key = storageKey(subjectId);
+  if (!key || typeof window === "undefined") return;
+  try {
+    window.localStorage.setItem(key, "confirmed");
+  } catch {
+    // Storage can be unavailable in privacy-restricted in-app browsers.
+  }
+}