Roichan-cloud/Photonic-Mixer-Remake ? reverse-engineered prompt

Build me a simple website for Photonic Mixer Remake that shows a friendly maintenance message for now, since the site is still being updated.

I want the main page to feel clean and branded, with the logo and a short note saying the site is coming back soon. Also include a proper 404 page, a basic old page for anything legacy, and a simple admin page if needed for future updates. Make it work nicely on mobile, and add the usual web app bits like a manifest and icons so it feels polished.

If you need to check anything current while setting it up, look up the latest docs online. Keep it lightweight, easy to edit later, and make sure the pages all load correctly without broken links.