I need a small web app that lets a visitor press an Upload button, choose a PDF, and have that file sent straight to the OpenAI GPT-4 API along with a prompt I will supply. Once the model finishes, the response should be turned into a fresh PDF that the user can immediately download from the same page—no other output format is required. Here is the full flow I have in mind: the user lands on the page, clicks the Upload button, selects a PDF, the server forwards both the file and my predefined prompt to GPT-4, waits for the response, converts that plain-text response into a nicely formatted PDF, and then shows a Download link. A simple progress indicator or spinner while the call is running will keep the interface clear. I’m happy with any modern stack—Python + Flask, Node + Express, or similar—as long as the codebase is clean, documented, and easy for me to extend. Please include the OpenAI integration, PDF generation (e.g., using reportlab, pdfkit, or another reliable library), and basic HTML/CSS/JS for the single-page interface. Acceptance criteria: • Upload button reliably handles standard-sized PDFs (up to ~10 MB). • The GPT prompt executes once per upload and returns the model’s full response. • The response is embedded in a new PDF and offered immediately for download. • All API keys and sensitive variables are read from environment variables, not hard-coded. • Clear README with setup steps so I can run the project locally and deploy to a small VPS later.