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>

deploy/README.md

@@ -14,17 +14,27 @@ Stack: gateway · identity · content · studio (.NET/Go) · file · render · n
                       mirror-nginx (:443, /etc/ssl/flatrender)
   flatrender.ir         → 171.22.25.73:1600  (fr2-frontend)
   api.flatrender.ir     → 171.22.25.73:1605  (fr2-gateway)
+  pay.flatrender.ir     → 171.22.25.73:1607  (fr2-payment, ZarinPal broker)
   storage.flatrender.ir → 171.22.25.73:1610  (fr2-minio)
 ```
 
+The **payment broker** (`fr2-payment`, `pay.flatrender.ir`) is a standalone generic
+ZarinPal gateway shared by FlatRender + meezi.ir + bargevasat.ir — ZarinPal only
+accepts callbacks on that one verified domain. It does NOT sit behind the API
+gateway (clients authenticate with an API key + HMAC). See
+[`PAYMENTS.md`](./PAYMENTS.md) for the integration contract. The `payment` schema
+is migration `31_payment_broker.sql` — on an existing DB volume it must be applied
+manually (migrations only auto-run on first volume creation):
+`docker exec -i fr2-postgres psql -U postgres -d flatrender < backend/db/migrations/31_payment_broker.sql`.
+
 ## One-time setup (do these BEFORE the first `git push gitea master`)
 
 1. **DNS** — this box sits BEHIND NAT: its interface IP is `171.22.25.73` (private),
    public NAT IPs are `31.171.101.127/.211`, and inbound 443 normally arrives via the
    edge/CDN `185.239.1.100` (same entry your other sites use, e.g. `meezi.ir`). So a new
    domain must enter the SAME way the others do — either:
-   - register `flatrender.ir` + `api` + `storage` + `www` in that edge/CDN (origin = this
-     server) and point DNS there, **or**
+   - register `flatrender.ir` + `api` + `pay` + `storage` + `www` in that edge/CDN (origin =
+     this server) and point DNS there, **or**
    - bypass the CDN and point DNS straight at the server's public IP (like the hokm `api`
      subdomain does — "must bypass").
    Pointing DNS at a random/registrar IP shows that host's default page (e.g. a "not
@@ -37,7 +47,7 @@ Stack: gateway · identity · content · studio (.NET/Go) · file · render · n
    cp <yourcert>/fullchain.pem  /etc/ssl/soroushasadi/flatrender/
    cp <yourcert>/privateKey.pem /etc/ssl/soroushasadi/flatrender/
    ```
-   Cert must cover `flatrender.ir` + `api.` + `storage.` (wildcard `*.flatrender.ir` + apex, or SAN).
+   Cert must cover `flatrender.ir` + `api.` + `pay.` + `storage.` (wildcard `*.flatrender.ir` + apex, or SAN).
 3. **mirror-nginx** — add the server blocks from [`mirror-nginx-flatrender.conf`](./mirror-nginx-flatrender.conf)
    to the proxy's `http{}` (the host file is `/root/mirror-server/nginx/nginx.conf`), then:
    `docker exec mirror-nginx nginx -t && docker exec mirror-nginx nginx -s reload`.
@@ -63,10 +73,11 @@ blocks (step 3) and visit `https://flatrender.ir`.
 
 ## Host ports (must be free on 171.22.25.73)
 
-`1600` frontend · `1605` gateway · `1610` MinIO · `1611` MinIO console. Postgres (5432)
-and render (5010) bind to `127.0.0.1` only. Avoid `:3000` (Gitea), `:8081-8083` (Nexus),
-`:1500/1505/1520` (bargevasat), `:3010/3101-3103/5080/5081` (meezi), `:3020`, `:2569`.
-Change them via `FRONTEND_PORT`/`GATEWAY_PORT`/`MINIO_PORT` in the secret if any collide.
+`1600` frontend · `1605` gateway · `1607` payment broker · `1610` MinIO · `1611` MinIO
+console. Postgres (5432) and render (5010) bind to `127.0.0.1` only. Avoid `:3000` (Gitea),
+`:8081-8083` (Nexus), `:1500/1505/1520` (bargevasat), `:3010/3101-3103/5080/5081` (meezi),
+`:3020`, `:2569`. Change them via `FRONTEND_PORT`/`GATEWAY_PORT`/`PAY_PORT`/`MINIO_PORT` in
+the secret if any collide.
 
 ## First-run notes