Upgrade SCSS code

[Maquinours]

Clear and concise description of the problem

Some deprecations have been added for SCSS code recently. This cause deprecation warnings like this :

DEPRECATION WARNING on line 1, column 9 of node_modules/.pnpm/react-big-calendar@1.15.0_react-dom@18.3.1_react@18.3.1__react@18.3.1/node_modules/react-big-calendar/lib/sass/agenda.scss: 
Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.
More info and automated migrator: https://sass-lang.com/d/import
  ╷
1 │ @import './variables';

or DEPRECATION WARNING: darken() is deprecated.

Suggested solution

Upgrade SASS version and replace deprecated uses by what is suggested.

Alternative

No response

Additional context

No response

Validations

• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Would you like to open a PR for this feature?

• I'm willing to open a PR