non-custodial Monero (XMR) for HikaShop on Joomla 5. derives a unique
subaddress per order and watches the chain read-only with the merchant's
view key; funds land straight in the merchant's wallet. no wallet-rpc, no
daemon.

- plg_hikashoppayment_xmrpay: the payment method. places the order pending
  on onAfterOrderConfirm, shows the branded payment card (amount, QR,
  address, live poll), and settles via a token-guarded poll endpoint.
- plg_task_xmrpaysettle: a Joomla 5 Scheduler task that sweeps pending
  orders in the background (Monero has no webhook).
- txid dedup via a UNIQUE table; the poll endpoint is HMAC-token guarded
  and refuses to answer for an unconfigured method.

the engine under engine/ is vendored from xmr-pay-php + the shared adapter
core; build via the xmr-pay-build packager. proven end to end against
stagenet (checkout poll + Web Cron sweep).