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/utf8/utf8.go

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2022 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 utf8
+
+import (
+    `github.com/bytedance/sonic/internal/rt`
+    `github.com/bytedance/sonic/internal/native/types`
+    `github.com/bytedance/sonic/internal/native`
+)
+
+// CorrectWith corrects the invalid utf8 byte with repl string.
+func CorrectWith(dst []byte, src []byte, repl string) []byte {
+    sstr := rt.Mem2Str(src)
+    sidx := 0
+
+    /* state machine records the invalid postions */
+    m := types.NewStateMachine()
+    m.Sp = 0 // invalid utf8 numbers
+
+    for sidx < len(sstr) {
+        scur  := sidx
+        ecode := native.ValidateUTF8(&sstr, &sidx, m)
+
+        if m.Sp != 0 {
+            if m.Sp > len(sstr) {
+                panic("numbers of invalid utf8 exceed the string len!")
+            }
+        }
+        
+        for i := 0; i < m.Sp; i++ {
+            ipos := m.Vt[i] // invalid utf8 position
+            dst  = append(dst, sstr[scur:ipos]...)
+            dst  = append(dst, repl...)
+            scur = m.Vt[i] + 1
+        }
+        /* append the remained valid utf8 bytes */
+        dst = append(dst, sstr[scur:sidx]...)
+
+        /* not enough space, reset and continue */
+        if ecode != 0 {
+            m.Sp = 0
+        }
+    }
+
+    types.FreeStateMachine(m)
+    return dst
+}
+
+// Validate is a simd-accelereated drop-in replacement for the standard library's utf8.Valid.
+func Validate(src []byte) bool {
+    return ValidateString(rt.Mem2Str(src))
+}
+
+// ValidateString as Validate, but for string.
+func ValidateString(src string) bool {
+    return native.ValidateUTF8Fast(&src) == 0
+}