ShenSeanChen/launch-DeepResearch-Backend ? reverse-engineered prompt

Build me a FastAPI backend for a deep research app that can take a user question, do a real research workflow, and stream the progress back live while it works. I want it to support OpenAI, Anthropic, and Kimi K2, with the user able to send their own API key instead of storing anything on the server. It should have a simple health check endpoint, a research streaming endpoint, and clear status updates like planning, researching, and final report.

Make it container ready so I can run it locally with Docker and deploy it to Cloud Run later. Please keep the code organized, add basic request validation, logging, and tests for the model connections and auth flow. If you need to check the latest docs for any model or deployment detail, go ahead and look them up online.