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/gin-gonic/gin/Makefile

@@ -0,0 +1,78 @@
+GO ?= go
+GOFMT ?= gofmt "-s"
+GO_VERSION=$(shell $(GO) version | cut -c 14- | cut -d' ' -f1 | cut -d'.' -f2)
+PACKAGES ?= $(shell $(GO) list ./...)
+VETPACKAGES ?= $(shell $(GO) list ./... | grep -v /examples/)
+GOFILES := $(shell find . -name "*.go")
+TESTFOLDER := $(shell $(GO) list ./... | grep -E 'gin$$|binding$$|render$$' | grep -v examples)
+TESTTAGS ?= ""
+
+.PHONY: test
+test:
+	echo "mode: count" > coverage.out
+	for d in $(TESTFOLDER); do \
+		$(GO) test $(TESTTAGS) -v -covermode=count -coverprofile=profile.out $$d > tmp.out; \
+		cat tmp.out; \
+		if grep -q "^--- FAIL" tmp.out; then \
+			rm tmp.out; \
+			exit 1; \
+		elif grep -q "build failed" tmp.out; then \
+			rm tmp.out; \
+			exit 1; \
+		elif grep -q "setup failed" tmp.out; then \
+			rm tmp.out; \
+			exit 1; \
+		fi; \
+		if [ -f profile.out ]; then \
+			cat profile.out | grep -v "mode:" >> coverage.out; \
+			rm profile.out; \
+		fi; \
+	done
+
+.PHONY: fmt
+fmt:
+	$(GOFMT) -w $(GOFILES)
+
+.PHONY: fmt-check
+fmt-check:
+	@diff=$$($(GOFMT) -d $(GOFILES)); \
+	if [ -n "$$diff" ]; then \
+		echo "Please run 'make fmt' and commit the result:"; \
+		echo "$${diff}"; \
+		exit 1; \
+	fi;
+
+.PHONY: vet
+vet:
+	$(GO) vet $(VETPACKAGES)
+
+.PHONY: lint
+lint:
+	@hash golint > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
+		$(GO) get -u golang.org/x/lint/golint; \
+	fi
+	for PKG in $(PACKAGES); do golint -set_exit_status $$PKG || exit 1; done;
+
+.PHONY: misspell-check
+misspell-check:
+	@hash misspell > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
+		$(GO) get -u github.com/client9/misspell/cmd/misspell; \
+	fi
+	misspell -error $(GOFILES)
+
+.PHONY: misspell
+misspell:
+	@hash misspell > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
+		$(GO) get -u github.com/client9/misspell/cmd/misspell; \
+	fi
+	misspell -w $(GOFILES)
+
+.PHONY: tools
+tools:
+	@if [ $(GO_VERSION) -gt 15 ]; then \
+		$(GO) install golang.org/x/lint/golint@latest; \
+		$(GO) install github.com/client9/misspell/cmd/misspell@latest; \
+	elif [ $(GO_VERSION) -lt 16 ]; then \
+		$(GO) install golang.org/x/lint/golint; \
+		$(GO) install github.com/client9/misspell/cmd/misspell; \
+	fi