refactor: migrate to Dart Sass and update SCSS structure

[daniil4udo]

Motivation for this PR is that FormKit uses this package and during the build sass is very "noisy" on deprecation warnings

• Replaced node-sass with sass in package.json for Dart Sass compatibility.
• Updated SCSS files to use the new Sass module system with @use and @forward.
• Refactored computed variables to use math and list modules for calculations.
• Adjusted mixins and functions to align with the new structure and improve readability.
• Ensured all breakpoints and variables are accessed through the new module system