feat(queue): 增加非文本模型分布式准入队列

使用 PostgreSQL 统一同步与异步非文本任务的并发准入、持久化等待和 Worker 容量分配，并将生产 API 与独立 Worker 角色拆分。

补充策略管理、共享契约、OpenAPI、Kubernetes 双节点 Worker 清单及跨节点验收脚本；未默认启用任何生产 queue_size 策略。

已在原基线完成 Go、前端、迁移、Shell、Kustomize 与长任务容量验收；合入最新主干后将重新执行发布门禁。

apps/api/internal/config/config.go

@@ -57,6 +57,8 @@ type Config struct {
 	GlobalHTTPProxySource                         string
 	LogLevel                                      slog.Level
 	BillingEngineMode                             string
+	ProcessRole                                   string
+	DatabaseMaxConns                              int
 	AsyncQueueWorkerEnabled                       bool
 	AsyncWorkerHardLimit                          int
 	AsyncWorkerRefreshIntervalSeconds             int
@@ -113,6 +115,8 @@ func Load() Config {
 		GlobalHTTPProxySource:             globalProxy.Source,
 		LogLevel:                          logLevel(env("LOG_LEVEL", "info")),
 		BillingEngineMode:                 strings.ToLower(env("BILLING_ENGINE_MODE", "observe")),
+		ProcessRole:                       strings.ToLower(strings.TrimSpace(env("AI_GATEWAY_PROCESS_ROLE", "all"))),
+		DatabaseMaxConns:                  envInt("AI_GATEWAY_DATABASE_MAX_CONNS", 0),
 		AsyncQueueWorkerEnabled:           env("AI_GATEWAY_ASYNC_QUEUE_WORKER_ENABLED", "true") == "true",
 		AsyncWorkerHardLimit:              envIntValidated("AI_GATEWAY_ASYNC_WORKER_HARD_LIMIT", 2048),
 		AsyncWorkerRefreshIntervalSeconds: envIntValidated("AI_GATEWAY_ASYNC_WORKER_REFRESH_INTERVAL_SECONDS", 5),
@@ -120,6 +124,14 @@ func Load() Config {
 }
 
 func (c Config) Validate() error {
+	switch strings.ToLower(strings.TrimSpace(c.ProcessRole)) {
+	case "", "all", "api", "worker":
+	default:
+		return errors.New("AI_GATEWAY_PROCESS_ROLE must be all, api, or worker")
+	}
+	if c.DatabaseMaxConns < 0 || c.DatabaseMaxConns > 1000 {
+		return errors.New("AI_GATEWAY_DATABASE_MAX_CONNS must be between 1 and 1000 when configured")
+	}
 	switch strings.ToLower(strings.TrimSpace(c.BillingEngineMode)) {
 	case "", "observe", "enforce", "hold":
 	default:
@@ -184,6 +196,33 @@ func (c Config) Validate() error {
 	return nil
 }
 
+func (c Config) EffectiveProcessRole() string {
+	role := strings.ToLower(strings.TrimSpace(c.ProcessRole))
+	if role == "" {
+		return "all"
+	}
+	return role
+}
+
+func (c Config) RunsPublicHTTP() bool {
+	return c.EffectiveProcessRole() != "worker"
+}
+
+func (c Config) RunsAsyncExecutionWorker() bool {
+	switch c.EffectiveProcessRole() {
+	case "api":
+		return false
+	case "worker":
+		return true
+	default:
+		return c.AsyncQueueWorkerEnabled
+	}
+}
+
+func (c Config) RunsBackgroundWorkers() bool {
+	return c.EffectiveProcessRole() != "api"
+}
+
 type GlobalHTTPProxyStatus struct {
 	HTTPProxy string
 	Source    string

apps/api/internal/config/config_test.go

@@ -94,6 +94,45 @@ func TestLoadAsyncQueueWorkerEnabled(t *testing.T) {
 	}
 }
 
+func TestProcessRolePrecedenceAndCompatibility(t *testing.T) {
+	t.Setenv("AI_GATEWAY_ASYNC_QUEUE_WORKER_ENABLED", "false")
+	cfg := Load()
+	if got := cfg.EffectiveProcessRole(); got != "all" {
+		t.Fatalf("legacy configuration changed process role to %q", got)
+	}
+	if cfg.RunsAsyncExecutionWorker() {
+		t.Fatal("legacy async worker disable was ignored")
+	}
+
+	t.Setenv("AI_GATEWAY_PROCESS_ROLE", "worker")
+	cfg = Load()
+	if got := cfg.EffectiveProcessRole(); got != "worker" {
+		t.Fatalf("effective process role = %q, want worker", got)
+	}
+	if cfg.RunsPublicHTTP() || !cfg.RunsAsyncExecutionWorker() || !cfg.RunsBackgroundWorkers() {
+		t.Fatalf("worker role capabilities are inconsistent: %+v", cfg)
+	}
+
+	t.Setenv("AI_GATEWAY_PROCESS_ROLE", "api")
+	cfg = Load()
+	if !cfg.RunsPublicHTTP() || cfg.RunsAsyncExecutionWorker() || cfg.RunsBackgroundWorkers() {
+		t.Fatalf("api role capabilities are inconsistent: %+v", cfg)
+	}
+}
+
+func TestValidateProcessRoleAndDatabasePool(t *testing.T) {
+	cfg := Load()
+	cfg.ProcessRole = "invalid"
+	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "PROCESS_ROLE") {
+		t.Fatalf("Validate() error = %v, want invalid process role", err)
+	}
+	cfg.ProcessRole = "api"
+	cfg.DatabaseMaxConns = -1
+	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "DATABASE_MAX_CONNS") {
+		t.Fatalf("Validate() error = %v, want invalid database max conns", err)
+	}
+}
+
 func TestValidateTaskHistorySettings(t *testing.T) {
 	cfg := Load()
 	cfg.TaskRetentionDays = 30