tanmayanalyst/promptpilot ? reverse-engineered prompt

Build me a full stack web app called PromptPilot that helps people turn rough prompt ideas into polished prompts they can actually use. I want a clean dark themed interface where someone can paste a short prompt, improve it with better structure and constraints, then run it against Google Gemini and see the live response, latency, and basic usage info.

It should also let users save and browse their past prompt runs, search and compare them, mark favorites, and export the history to CSV. Add a simple template library for common use cases like coding, marketing, business, reasoning, and data, with fields that users can fill in quickly.

Please include a settings area where someone can add and verify their Gemini API key, and make the app remember it locally. Build the backend endpoints needed for health checks, key verification, prompt optimization, and running prompts. If you need to look up current Gemini API docs online, do that.