Use path alias for imports and update folder structure in /ui

Closes #3452489

This MR does two things:

1. Uses path aliases for the top level directories inside /ui/src so instead of doing import foo from ../../app/hooks we can now just do import foo from @/app/hooks.
2. Minor folder structure changes based on https://redux.js.org/style-guide/#:~:text=Structure%20Files%20as%20Feature%20Folders,the%20%22ducks%22%20pattern).
   1. Moved the root component App.tsx an App.module.css to /app
   2. Moved /list and /panel directories to /components.

My proposal for the file structure is to separate Redux-related components in /features from regular components /components .