Reconcile a rejected admin refund against the real EveryPay state

[acirtautas]

Problem

A refund made in the EveryPay merchant portal makes the admin Refund button fail with a generic "refund failed" flash until the portal callback is processed: EveryPay rejects the API refund (the amount exceeds what is standing), and that rejection was indistinguishable from a real failure - the payment stayed completed even though the money had already been reimbursed.

Change

RefundEveryPayPaymentHandler now treats a 4xx rejection as a hint only:

• it re-reads GET /v4/payments/{payment_reference} - the same authenticated call the synchronizer uses, so no state change ever derives from an error response;
• when EveryPay confirms refunded, the in-flight completed -> refunded transition completes with the fresh payment snapshot (the listener and its transaction are untouched - the commit path is exactly today's success path);
• any other remote state, a failing re-read, a 5xx or a transport error rethrows the original rejection: rollback, error flash, payment stays completed in the database.

The remote-snapshot merge (payment_state/payment_method/standing_amount/synchronized_at) is now shared between the synchronizer and the refund handler via EveryPayGateway::withRemoteSnapshot(), so both write the same details shape.

Known trade-off (documented in the code): EveryPay reports refunded for partial portal refunds too, so a partial portal refund reconciles the Sylius payment to refunded - the same thing the callback path already does; standing_amount in the snapshot keeps the remainder visible on the admin order page.

Tests

• 9 new unit cases: reconciliation across 400/404/422, rejection kept for non-refunded remote states, no re-read on 5xx/transport failures, original rejection preserved when the re-read itself fails.
• 2 new Behat scenarios next to the portal-refund loop guard: a rejected refund that reconciles, and a rejected refund with the money still in place that stays rejected.

Gates

phpunit (both suites), phpstan level 9, ecs, behat --strict - all green, also under composer update --prefer-lowest --prefer-stable.