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/bytedance/sonic/unquote/unquote.go

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2021 ByteDance Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package unquote
+
+import (
+    `unsafe`
+    `runtime`
+
+    `github.com/bytedance/sonic/internal/native`
+    `github.com/bytedance/sonic/internal/native/types`
+    `github.com/bytedance/sonic/internal/rt`
+)
+
+// String unescapes a escaped string (not including `"` at begining and end)
+// It validates invalid UTF8 and replace with `\ufffd`
+func String(s string) (ret string, err types.ParsingError) {
+    mm := make([]byte, 0, len(s))
+    err = intoBytesUnsafe(s, &mm, true)
+    ret = rt.Mem2Str(mm)
+    return
+}
+
+// IntoBytes is same with String besides it output result into a buffer m
+func IntoBytes(s string, m *[]byte) types.ParsingError {
+    if cap(*m) < len(s) {
+        return types.ERR_EOF
+    } else {
+        return intoBytesUnsafe(s, m, true)
+    }
+}
+
+// String unescapes a escaped string (not including `"` at begining and end)
+//   - replace enables replacing invalid utf8 escaped char with `\uffd`
+func _String(s string, replace bool) (ret string, err error) {
+    mm := make([]byte, 0, len(s))
+    err = intoBytesUnsafe(s, &mm, replace)
+    ret = rt.Mem2Str(mm)
+    return
+}
+
+func intoBytesUnsafe(s string, m *[]byte, replace bool) types.ParsingError {
+    pos := -1
+    slv := (*rt.GoSlice)(unsafe.Pointer(m))
+    str := (*rt.GoString)(unsafe.Pointer(&s))
+
+    flags := uint64(0)
+    if replace {
+        /* unquote as the default configuration, replace invalid unicode with \ufffd */
+        flags |= types.F_UNICODE_REPLACE
+    }
+
+    ret := native.Unquote(str.Ptr, str.Len, slv.Ptr, &pos, flags)
+
+    /* check for errors */
+    if ret < 0 {
+        return types.ParsingError(-ret)
+    }
+
+    /* update the length */
+    slv.Len = ret
+    runtime.KeepAlive(s)
+    return 0
+}
+
+
+