feat(billing): 支付 P5.2 —— 微信支付 Native 渠道（扫码充值）

wechatpay-go v0.2.21。凭据全 env 注入(WECHAT_MCHID/MCH_CERT_SERIAL/
MCH_PRIVATE_KEY/APIV3_KEY/APPID/NOTIFY_URL),缺一渠道即隐藏——半配置/假凭据
只打日志不拖垮 gateway(用假私钥实测过降级)。

- internal/payment:Native 下单出 code_url、APIv3 回调验签解密、主动查单,
  三者统一收敛为 QueryResult。
- 下单 POST /billing/orders {pack_id}(≥member+审计):金额/积分按在售包服务端
  锁定进订单行,不信任客户端;渠道下单失败即作废,不留付不了的 pending。
- 到账两条路汇入同一个 MarkOrderPaid 幂等闸(CAS+唯一索引双闸,同 P5.1):
  ①公开回调路由(验签是唯一的门;金额与订单不符不入账);②前端轮询的
  GET /billing/orders/:id 在 pending 时顺路主动查单——本地/内网收不到公网
  回调也能确认到账,回调只是生产更快的通道。pending 超 30 分钟置 expired。
- Web 面:在售包卡片(渠道亮才出现)→扫码弹窗(qrcode 画 code_url,二维码底色
  固定纯白——暗色主题下低对比码扫不出来)→2.5s 轮询→到账 toast+刷余额。

验证:go/tsc/vitest 全绿;无凭据+假凭据两种降级 live 四连
(channels 只剩 redeem/下单 400 引导兑换码/回调 503/兑换码闭环不受影响)。
⚠️ 真通道(prepay→扫码→回调/查单→入账)需真实商户号,未 live——用户配好
env 后用小额包实测,建议先配 ¥0.01 测试包走一单。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-gateway/go.mod

@@ -11,6 +11,8 @@ require (
 	github.com/prometheus/client_golang v1.23.2
 	github.com/redis/go-redis/v9 v9.20.0
 	github.com/sundynix/sundynix-shared v0.0.0
+	github.com/wechatpay-apiv3/wechatpay-go v0.2.21
+	go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin v0.69.0
 	golang.org/x/crypto v0.53.0
 	gorm.io/driver/postgres v1.6.0
 	gorm.io/gorm v1.31.1
@@ -23,6 +25,7 @@ require (
 	github.com/bytedance/gopkg v0.1.4 // indirect
 	github.com/bytedance/sonic v1.15.1 // indirect
 	github.com/bytedance/sonic/loader v0.5.1 // indirect
+	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cloudwego/base64x v0.1.7 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
@@ -35,6 +38,7 @@ require (
 	github.com/goccy/go-json v0.10.6 // indirect
 	github.com/goccy/go-yaml v1.19.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.29.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/pgx/v5 v5.6.0 // indirect
@@ -45,7 +49,6 @@ require (
 	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
 	github.com/klauspost/crc32 v1.3.0 // indirect
-	github.com/kr/text v0.2.0 // indirect
 	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
 	github.com/mattn/go-isatty v0.0.22 // indirect
@@ -71,10 +74,13 @@ require (
 	github.com/zeebo/xxh3 v1.1.0 // indirect
 	go.mongodb.org/mongo-driver/v2 v2.6.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
-	go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin v0.69.0 // indirect
 	go.opentelemetry.io/otel v1.44.0 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.44.0 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.44.0 // indirect
 	go.opentelemetry.io/otel/metric v1.44.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.44.0 // indirect
 	go.opentelemetry.io/otel/trace v1.44.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
 	go.uber.org/atomic v1.11.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
@@ -83,7 +89,9 @@ require (
 	golang.org/x/sync v0.21.0 // indirect
 	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/text v0.38.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20260618152121-87f3d3e198d3 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20260618152121-87f3d3e198d3 // indirect
+	google.golang.org/grpc v1.81.1 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
 	gopkg.in/ini.v1 v1.67.2 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 )