Remove unused dependencies and add missing dayjs (#265)

- Remove unused packages: react-router-dom, react-swipeable, react-intersection-observer, d3-scale-chromatic, cookies
- Remove unused dev dependencies: @types/jest, @types/d3-interpolate
- Add missing dayjs dependency that was being imported
- Keep @types/cookie as it's needed by session.ts
- Build and lint tests pass

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <[email protected]>

Author: marcodejongh