Live supplier reservation details for a booking

Runs booking.getSupplierReservation; owner-only. Fetched live from the supplier on every call, so render it as its own section rather than blocking the booking screen. Never fails on a supplier problem: available: false (with diagnostics) covers an unconfirmed booking, a supplier without reservation lookup, an outage, and the first two minutes after booking, when the supplier forbids the lookup — refetch later. available: true adds voucherIssued, invoiceNumber, roomCount, supplierConfirmationNumber and bookingStatus, each nullable.