Launch mode, configured payment methods and sellable supply (ports and per-GB traffic)

mode is waitlist while ports are not on sale (buy buttons become "Notify me"). payment_methods lists only methods whose credentials are configured; wallet is per customer and appears in GET /checkout/methods instead. seller is the configured seller identity (SELLER_*, SUPPORT_EMAIL, ABUSE_EMAIL, BRAND_NAME): type null means no registered business is claimed, vat_registered false means VAT is 0 on every order. traffic_validity_days 0 means GB never expire. ports_on_sale true means partner ports can be bought by everyone (PORTS_ON_SALE on and not in waitlist mode).