Add screenshots of the mockups made with Claude Design to `docs/design/`, and link to them from the README and `USER_INTERFACE.md`. The mockups only give a visual impression of the idea. They are not the final design. **Done when:** - [ ] Screenshots of all mockup pages are in `docs/design/` - [ ] `docs/design/README.md` explains what the mockups show and that they are not final - [ ] The README and `USER_INTERFACE.md` link to the mockups