perf(queue): 按策略动态扩缩异步 Worker

将 River 执行容量按平台模型与用户组的有效并发策略动态调整，并为长任务续租、并发租约原子抢占和限流退避补充保护。\n\n统一平台模型限流继承语义，兼容历史 platformLimits/modelLimits，并为三个迁移图像模型建立独立并发租约。补充管理端显式继承/覆盖配置、指标、单元测试及隔离 PostgreSQL 验收。\n\n验证：go test ./... -count=1；pnpm lint；pnpm test；pnpm build；隔离 PostgreSQL 并发原子性/续租测试；128 任务与三分钟长任务动态 Worker 验收。

apps/api/internal/config/config_test.go

@@ -26,7 +26,7 @@ func TestLoadIdentitySecretStoreUsesNewEnvironmentNamesAndIgnoresLegacyBusinessV
 }
 
 func TestValidateIdentityFileSecretStoreRequiresDirectory(t *testing.T) {
-	cfg := Config{IdentitySecretStore: "file"}
+	cfg := Config{IdentitySecretStore: "file", AsyncWorkerHardLimit: 2048, AsyncWorkerRefreshIntervalSeconds: 5}
 	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "IDENTITY_SECRET_DIR") {
 		t.Fatalf("Validate() error = %v, want missing identity secret directory", err)
 	}
@@ -37,7 +37,12 @@ func TestValidateIdentityFileSecretStoreRequiresDirectory(t *testing.T) {
 }
 
 func TestValidateIdentityKubernetesSecretStore(t *testing.T) {
-	cfg := Config{IdentitySecretStore: "kubernetes", IdentityKubernetesSecretName: "easyai-gateway-identity"}
+	cfg := Config{
+		IdentitySecretStore:               "kubernetes",
+		IdentityKubernetesSecretName:      "easyai-gateway-identity",
+		AsyncWorkerHardLimit:              2048,
+		AsyncWorkerRefreshIntervalSeconds: 5,
+	}
 	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "namespace") {
 		t.Fatalf("Validate() error = %v, want missing namespace", err)
 	}
@@ -52,8 +57,27 @@ func TestValidateIdentitySecurityEventTiming(t *testing.T) {
 		IdentitySecurityEventHeartbeatIntervalSeconds: 60,
 		IdentitySecurityEventStaleAfterSeconds:        60,
 		IdentitySecurityEventClockSkewSeconds:         60,
+		AsyncWorkerHardLimit:                          2048,
+		AsyncWorkerRefreshIntervalSeconds:             5,
 	}
 	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "heartbeat") {
 		t.Fatalf("Validate() error = %v, want invalid stale threshold", err)
 	}
 }
+
+func TestValidateAsyncWorkerSettings(t *testing.T) {
+	cfg := Config{AsyncWorkerHardLimit: 10001, AsyncWorkerRefreshIntervalSeconds: 5}
+	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "HARD_LIMIT") {
+		t.Fatalf("Validate() error = %v, want invalid hard limit", err)
+	}
+	cfg.AsyncWorkerHardLimit = 2048
+	cfg.AsyncWorkerRefreshIntervalSeconds = 0
+	if err := cfg.Validate(); err == nil || !strings.Contains(err.Error(), "REFRESH_INTERVAL") {
+		t.Fatalf("Validate() error = %v, want invalid refresh interval", err)
+	}
+	t.Setenv("AI_GATEWAY_ASYNC_WORKER_HARD_LIMIT", "not-an-integer")
+	loaded := Load()
+	if err := loaded.Validate(); err == nil || !strings.Contains(err.Error(), "HARD_LIMIT") {
+		t.Fatalf("Validate() error = %v, want invalid non-integer hard limit", err)
+	}
+}