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_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