CI: End-to-end tests for async

Is your feature request related to a problem?
We currently lack end-to-end CI tests for the async pipeline, which leads to unnoticed regressions impacting customers. Without monitoring and alerting, issues may persist before they are detected.

Describe the solution you'd like

• Add end-to-end CI tests for the async pipeline using a dedicated test account.
• Run tests every 5 minutes on /llm/call, /llm/chain, and collection/document flows.
• Verify job completion within SLA, validate responses, and ensure correct callback delivery.
• Implement alerts for failures or latency breaches.
• Track success rate, latency, and callback delivery in dashboards.
• Run these tests on every PR and block merges if they fail.

Empieza trazando la canalización asíncrona detrás de /llm/call, /llm/chain y los flujos de colecciones/documentos; después, revisa la configuración de CI existente y los puntos de entrada de las pruebas. Se considera terminado cuando las comprobaciones end-to-end programadas y por PR verifican el cumplimiento del SLA, las respuestas y los callbacks, con alertas de fallos o latencia y paneles para la tasa de éxito, la latencia y la entrega de callbacks.