fix(runner): 稳定异步任务重启恢复

避免恢复任务将已到期的 next_run_at 误插入 River scheduled 状态，并使用专用模型隔离重启集成测试。\n\n验证：Go 全量测试、govulncheck、pnpm lint/test/build/audit、Compose、镜像、迁移、流水线及 SemVer 门禁全部通过。

apps/api/internal/httpapi/core_flow_integration_test.go

@@ -1654,6 +1654,17 @@ WHERE m.platform_id = $1::uuid
 		t.Fatal("task progress callback outbox should receive events")
 	}
 
+	restartModel := "worker-restart-" + suffixText
+	createSimulationTextPlatformModel(
+		t,
+		server.URL,
+		loginResponse.AccessToken,
+		"openai-worker-restart-"+suffixText,
+		"OpenAI Worker Restart",
+		restartModel,
+		1,
+		nil,
+	)
 	var restartAsyncTask struct {
 		TaskID string `json:"taskId"`
 		Task   struct {
@@ -1663,7 +1674,7 @@ WHERE m.platform_id = $1::uuid
 		} `json:"task"`
 	}
 	doJSONWithHeaders(t, server.URL, http.MethodPost, "/api/v1/responses", apiKeyResponse.Secret, map[string]any{
-		"model":                defaultTextModel,
+		"model":                restartModel,
 		"runMode":              "simulation",
 		"simulation":           true,
 		"simulationDurationMs": 2000,