Description

The codebase currently uses deprecated Sass @import statements which will be removed in Dart Sass 3.0.0. We need to update these to use the modern @use syntax.

Current Behavior

• Sass files use deprecated @import statements
• Mixins and variables are globally available without namespacing
• Extend statements may fail if placeholders aren't found
• Storybook shows deprecation warnings

Expected Behavior

• All Sass files should use @use instead of @import
• Mixins and variables should be properly namespaced
• Extend statements should be made optional with !optional flag
• No deprecation warnings in Storybook