Refactor vanilla CSS to TailwindCSS

# Refactor vanilla CSS to TailwindCSS

The project uses Bootstrap and vanilla CSS for the styling of the web application. The goal of this issue is to refactor the vanilla CSS to TailwindCSS, a utility-first CSS framework that offers more consistency and performance. This will involve converting the existing CSS files to TailwindCSS, updating the TailwindCSS configuration file, and purging the unused classes from the production build.

## Acceptance criteria

- The appearance and functionality of the project are not affected by the conversion.
- The Bootstrap framework is still used for the layout and components of the project.
- The TailwindCSS configuration file is updated with the custom colors, fonts, and breakpoints of the project.
- The unused TailwindCSS classes are purged from the production build using the [PurgeCSS](https://github.com/FullHuman/purgecss) tool.