Batch Send — pay 2 to 8 addresses with one signature, all or nothing (free; unsigned Batch + Xaman request)

Body { from, recipients: [{ address, amount, currency: XRP|RLUSD, destinationTag? }] }. Every payment is checked on the live ledger first (destination exists or will be created, destination tag, Deposit Authorization, RLUSD trust line, sender balance + fee); a batch that would fail is refused (422) with per-recipient problems. Returns ONE unsigned XRPL Batch (tfAllOrNothing) with one Payment per recipient, plus a Xaman sign request. Outer fee = (2 + n) × the open-ledger fee. Sign before any other transaction from the sender (it uses the next sequence numbers). Free; XRPLHub never signs. Amendment-gated on BatchV1_1 at request time.