feat: Gateway store 桩换真实 GORM/Postgres + go-redis (含自动迁移与优雅降级)

第 2 层网关持久层落地，遵守 sundynix_ 表名前缀 + AutoMigrate 约定。

- store: GORM(NamingStrategy 前缀 sundynix_/单数) → User=sundynix_user, Task=sundynix_task
  启动 AutoMigrate；go-redis/v9 滑动窗口限流(Incr+Expire,按 IP)
- 优雅降级：连不上库则 warn 继续(不 fatal)，保证无 Docker 的 make demo 仍跑通
- handler: SubmitTask 持久化任务(best-effort)，Billing 真实读库返回 tasks_submitted
- main: OpenPostgres/OpenRedis 读 POSTGRES_DSN/REDIS_ADDR 环境变量
- 验证: 4 模块 build ✓；e2e 3 测试 PASS；live 双路径(真实库持久化 + 坏DSN降级)实测通过

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

sundynix-gateway/go.mod

@@ -1,10 +1,13 @@
 module github.com/sundynix/sundynix-gateway
 
-go 1.23
+go 1.24
 
 require (
 	github.com/gin-gonic/gin v1.10.0
+	github.com/redis/go-redis/v9 v9.20.0
 	github.com/sundynix/sundynix-shared v0.0.0
+	gorm.io/driver/postgres v1.6.0
+	gorm.io/gorm v1.31.1
 )
 
 replace github.com/sundynix/sundynix-shared => ../sundynix-shared
@@ -12,6 +15,7 @@ replace github.com/sundynix/sundynix-shared => ../sundynix-shared
 require (
 	github.com/bytedance/sonic v1.11.6 // indirect
 	github.com/bytedance/sonic/loader v0.1.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cloudwego/base64x v0.1.4 // indirect
 	github.com/cloudwego/iasm v0.2.0 // indirect
 	github.com/gabriel-vasile/mimetype v1.4.3 // indirect
@@ -20,10 +24,16 @@ require (
 	github.com/go-playground/universal-translator v0.18.1 // indirect
 	github.com/go-playground/validator/v10 v10.20.0 // indirect
 	github.com/goccy/go-json v0.10.2 // 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
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	github.com/jinzhu/inflection v1.0.0 // indirect
+	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.17.9 // indirect
-	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
-	github.com/kr/pretty v0.3.0 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.10 // indirect
+	github.com/kr/text v0.2.0 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
@@ -32,14 +42,16 @@ require (
 	github.com/nats-io/nkeys v0.4.7 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/rogpeppe/go-internal v1.6.1 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.12 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
 	golang.org/x/arch v0.8.0 // indirect
-	golang.org/x/crypto v0.27.0 // indirect
+	golang.org/x/crypto v0.31.0 // indirect
 	golang.org/x/net v0.25.0 // indirect
-	golang.org/x/sys v0.25.0 // indirect
-	golang.org/x/text v0.18.0 // indirect
+	golang.org/x/sync v0.10.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
+	golang.org/x/text v0.21.0 // indirect
 	google.golang.org/protobuf v1.34.1 // indirect
-	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )