non-custodial Monero (XMR) for VirtueMart 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_vmpayment_xmrpay: the payment method (vmPSPlugin). places the order
  pending on plgVmConfirmedOrder, renders the branded payment card via the
  post_payment layout, and settles via a token-guarded poll endpoint.
- plg_task_xmrpaysettle_vm: a Joomla 5 Scheduler task that sweeps pending
  orders in the background.
- per-order scan state in the plugin's own table; txid dedup via a UNIQUE
  column claimed with UPDATE ... WHERE xmr_txid IS NULL; the poll endpoint
  is HMAC-token guarded and refuses 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 (full checkout + Web Cron sweep).