ansukhan164-rgb/NEXUS-AI-Chatbot ? reverse-engineered prompt

Build me a polished AI chatbot web app called NEXUS AI with a futuristic premium look and a smooth, modern chat experience. I want users to open the site, chat with Gemini powered responses, see their conversation history, and switch between dark mode and light mode. Please include a voice assistant so the app can listen and speak, and make the interface feel fast, responsive, and mobile friendly.

Use a simple Flask backend with a clean front end using HTML, CSS, and JavaScript. Keep the app easy to run locally with environment variables for the API key, and make sure the structure is clean enough to deploy in Docker too. If anything about the Gemini setup or voice features needs current docs, look them up online and wire it up properly. The end result should feel like a real production ready chatbot, not a basic demo.