WordPress custom taxonomy not showing

   $terms = get_terms(
    array(
        'taxonomy'   => 'career',
        'hide_empty' => false,
    )
);

Your taxonomy isn’t called career. Your taxonomy is called (confusingly) categories.

If you check the docs, you’ll see the second argument passed to register_taxonomy is the object type (eg, post, my_cpt) that the tax is to be used on. So in your registration you are creating a taxonomy called categories that will be used on the career post type.