Remove NextUI dependency (and maybe Tailwind)

[vgeorge]

In #740 we worked on a fix to avoid changing the environment page style caused by NextUI.

In that PR we moved the tailwind @base directive, which injects NextUI plugin styles, to the scope of the .lonboard div. We also added some hard-coded styles from NextUI to that div.

Considering that a change in the NextUI package might break this implementation, this is not a very maintainable solution. Also, we don't expect many different components to be present in the widget, so a component library might be overkill.

At the moment, I'm leaning towards removing it as a dependency and implementing custom styles, relying only on Tailwind or even removing it to avoid unintended side effects.

cc @kylebarron @Bjoern-Rapp