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/leodido/go-urn/scim.go

@@ -0,0 +1,48 @@
+package urn
+
+import (
+	"encoding/json"
+	"fmt"
+
+	scimschema "github.com/leodido/go-urn/scim/schema"
+)
+
+const errInvalidSCIMURN = "invalid SCIM URN: %s"
+
+type SCIM struct {
+	Type  scimschema.Type
+	Name  string
+	Other string
+	pos   int
+}
+
+func (s SCIM) MarshalJSON() ([]byte, error) {
+	return json.Marshal(s.String())
+}
+
+func (s *SCIM) UnmarshalJSON(bytes []byte) error {
+	var str string
+	if err := json.Unmarshal(bytes, &str); err != nil {
+		return err
+	}
+	// Parse as SCIM
+	value, ok := Parse([]byte(str), WithParsingMode(RFC7643Only))
+	if !ok {
+		return fmt.Errorf(errInvalidSCIMURN, str)
+	}
+	if value.RFC() != RFC7643 {
+		return fmt.Errorf(errInvalidSCIMURN, str)
+	}
+	*s = *value.SCIM()
+
+	return nil
+}
+
+func (s *SCIM) String() string {
+	ret := fmt.Sprintf("urn:ietf:params:scim:%s:%s", s.Type.String(), s.Name)
+	if s.Other != "" {
+		ret += fmt.Sprintf(":%s", s.Other)
+	}
+
+	return ret
+}