chore: update examples for Next.js 16 + React 19

integrate-with-next:
- Next.js 15 → 16, React 18 → 19, TypeScript 4.9 → 5.6
- Remove unused @next/font dependency
- Upgrade @testing-library/dom to v10, jest-dom to v6
- Upgrade @types/node to 22, @types/react to 19
- Update test snapshot for React 19

integrate-with-react:
- React 18 → 19
- Upgrade @testing-library/react to v16, user-event to v14

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jonaslagoni