`customer.points_expire_at` on loyalty webhook events

Product Potential Points — Added reference/product-potential-points-api-settings.json (storefront …/loyalty, POST product_potential_points and POST customer_product_potential_points with auth headers). Removed that path from reference/api-settings.json.
points_expire_at in reference/api-settings.json — New components.schemas.CustomerPointsExpireAt (expiration policies, webhook links, REST parity). GET /api/v2/customers/recent customer items and GET /api/v2/customers 200 schema reference it.
Ten webhook pages (referral-completed, loyalty-opt-in-1, customer-birthday-captured, redemption-cancellation-request, customer-anniversary-captured, redemption-reminder-1, referral-link-share, referral-share-reminder, referral-completed-new, points-earned) — JSON samples include points_expire_at with an ISO example where expiration applies; in-page customer.points_expire_at notes policies, null for Never expire, and REST parity. No long copy on intro-to-webhook-events.md.
Customer docs — fetch-customer-details.md and fetch-all-recently-updated-customers.md mention points_expire_at and link to Points Earned for the full field write-up.