chore: add more eslint rules

[eglitise]

Here are a few enhancements to the ESLint configuration, since it was recently edited for migration to flat config:

• Use React plugin's jsx-runtime config and remove the React exclusion for no-unused-vars. This allowed the removal of all the empty import React from 'react'; lines, which also reduced the production app bundle size.
• Add a plugin for sorting imports. A while back, a Prettier plugin was used to achieve this, but this approach is simpler.