Refactoring: SASS `@import` is deprecated

[deleonio]

We must replace all @import's in our SCSS-Files with @use.

We should make some PRs for every style module:

• base style in components
• Styles in der Sample App
• theme default
• theme bwst
• theme eu-*

Den Regex zum ersetzen im Ticket hinterlegen, falls möglich.

[anicyne]

Regex :

@import\s+(['"])(.*?)\1;
@use $1$2$1 as *;