[WIP] refactor frontend

## Is your feature request related to a problem? Please describe

Adjust the tech stack.

## Description of the new feature/enhancement

Adapt to new tech stack.

## Proposed technical implementation details (optional)

- pnpm
- next.js
- react
- tailwind
- headlessui
- cypress
- jest
- react-query
- esbuild(optional)

## Additional context

Start by reviewing the open linked pull request #32 and the frontend entry points it changes. Compare its implementation with the proposed Next.js, React, Tailwind, and Cypress stack; the work is done when the frontend has been adapted to the agreed stack and its tests pass.

Written by the indexing model from the issue text.