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.

Inizia tracciando la pipeline asincrona alla base di /llm/call, /llm/chain e dei flussi di collection/document, quindi esamina la configurazione CI esistente e i punti di ingresso dei test. Il lavoro è completato quando i controlli end-to-end pianificati e per PR verificano il rispetto dello SLA, le risposte e i callback, con avvisi per errori o latenza e dashboard per la percentuale di successo, la latenza e la consegna dei callback.