Migrate away from SCSS `@import`

[`@import` is now officially deprecated](https://sass-lang.com/blog/import-is-deprecated/) so we would need to migrate to `@use`. They even also provide a [Migrator](https://sass-lang.com/blog/import-is-deprecated/#migrator).

see also https://github.com/db-ui/base/issues/593