feat(payment): standalone ZarinPal broker on pay.flatrender.ir

A generic multi-client payment gateway so FlatRender, meezi.ir and
bargevasat.ir can all pay through ZarinPal's single verified callback
domain (pay.flatrender.ir).

New Go service services/payment (clones the notification skeleton +
vendored deps):
- migration 31_payment_broker.sql — `payment` schema: client_apps,
  transactions, webhook_deliveries.
- ZarinPal v4 client ported from the proven identity PaymentService
  (request.json -> StartPay -> verify.json; codes 100/101).
- client API: POST /v1/pay/request + /v1/pay/inquiry, authed by
  X-Api-Key + HMAC body signature; GET /callback/zarinpal (the single
  verified endpoint) verifies, then 302s the user back to the site's
  return_url (signed) and fires a signed, retried webhook.
- per-client ZarinPal merchant override (default = shared merchant);
  amount stored canonically in Rial, unit to ZarinPal env-configurable.
- admin API /v1/admin/* (FlatRender admin JWT): client-app CRUD +
  key issue/rotate + transactions list.

Deploy wiring: payment-svc in docker-compose.v2.yml (host port 1607),
pay.flatrender.ir server block in mirror-nginx conf, ENV_FILE +
README updates (cert SAN + manual migration note).

Admin UI: src/components/admin/PaymentsAdmin.tsx (client apps with
one-time key reveal + rotate, transactions table) + /admin/payments
page + nav link + fa/en strings; pay-admin proxy route to payment-svc.

Docs/SDK: deploy/PAYMENTS.md (integration contract) + deploy/sdk/flatpay.js
(zero-dep Node client + webhook verifier) for meezi/any site.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/payment/vendor/github.com/google/uuid/CHANGELOG.md

@@ -0,0 +1,41 @@
+# Changelog
+
+## [1.6.0](https://github.com/google/uuid/compare/v1.5.0...v1.6.0) (2024-01-16)
+
+
+### Features
+
+* add Max UUID constant ([#149](https://github.com/google/uuid/issues/149)) ([c58770e](https://github.com/google/uuid/commit/c58770eb495f55fe2ced6284f93c5158a62e53e3))
+
+
+### Bug Fixes
+
+* fix typo in version 7 uuid documentation ([#153](https://github.com/google/uuid/issues/153)) ([016b199](https://github.com/google/uuid/commit/016b199544692f745ffc8867b914129ecb47ef06))
+* Monotonicity in UUIDv7 ([#150](https://github.com/google/uuid/issues/150)) ([a2b2b32](https://github.com/google/uuid/commit/a2b2b32373ff0b1a312b7fdf6d38a977099698a6))
+
+## [1.5.0](https://github.com/google/uuid/compare/v1.4.0...v1.5.0) (2023-12-12)
+
+
+### Features
+
+* Validate UUID without creating new UUID ([#141](https://github.com/google/uuid/issues/141)) ([9ee7366](https://github.com/google/uuid/commit/9ee7366e66c9ad96bab89139418a713dc584ae29))
+
+## [1.4.0](https://github.com/google/uuid/compare/v1.3.1...v1.4.0) (2023-10-26)
+
+
+### Features
+
+* UUIDs slice type with Strings() convenience method ([#133](https://github.com/google/uuid/issues/133)) ([cd5fbbd](https://github.com/google/uuid/commit/cd5fbbdd02f3e3467ac18940e07e062be1f864b4))
+
+### Fixes
+
+* Clarify that Parse's job is to parse but not necessarily validate strings. (Documents current behavior)
+
+## [1.3.1](https://github.com/google/uuid/compare/v1.3.0...v1.3.1) (2023-08-18)
+
+
+### Bug Fixes
+
+* Use .EqualFold() to parse urn prefixed UUIDs ([#118](https://github.com/google/uuid/issues/118)) ([574e687](https://github.com/google/uuid/commit/574e6874943741fb99d41764c705173ada5293f0))
+
+## Changelog