Price a hotel checkout before payment

Runs payment.getHotelCheckoutQuote. Public by design — it is the price-on-load half of the guest-capable payment-first checkout (critical decision #4), and it is the same call the web checkout makes when its form mounts. Pure read: no PaymentIntent, no payment row, no booking. Call it as the checkout screen loads so the real supplier tax/fee split, add-ons, promo outcome and rateValidUntil are on screen BEFORE the customer commits to paying, then send the same pricing fields to POST /v1/payments/hotel-checkout-intent. POST rather than GET because the input carries a supplier room id up to 8 KB. Signed-in callers also get their saved cards; staff accounts get simulated: true.