chore: remove intermdiate base variables in favour of inline utils

[farazcsk]

E.g.

@utility bg-muted {
  background-color: var(--bg-muted);
}

becomes

@utility bg-muted {
  background-color: var(--color-neutral-100);
  
  @variant dark {
    background-color: var(--color-neutral-900);
  }
}

[linear]

DES-358 Refactor tailwind utility definitions