[FrancescoMolinaro]

References

Issue: #6457

Description

Replace hardcoded colors with bootstrap or custom variables.
Add linter for scss, libraries added for the purpose:

https://www.npmjs.com/package/stylelint
https://www.npmjs.com/package/stylelint-scss
https://www.npmjs.com/package/postcss-scss

Instructions for Reviewers

There should't be any fixed color in component's stylesheets.
The new script lint:scss should list errors in case some colors are present in component's stylesheets but it should allow them in the variables stylesheets.

List of changes in this PR:

Migrated fixed colors to bootstrap or custom variables.
Added linters and utility library.
Configured script to lint files.

AI Disclosure (REQUIRED)

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Were AI tools used in the creation of this PR?

• No (This PR does NOT include AI-generated or AI-assisted content that requires disclosure.)
• Yes (This PR includes AI-generated or AI-assisted content that requires disclosure.)

If "Yes", briefly describe what portion of this PR was generated or assisted by AI. Additionally, tell us how you've verified the AI output aligns with DSpace's coding standards and is secure and accurate.

(Example: "AI assisted me in investigating the bug and generated a suggested patch. I reviewed, modified and tested the code. No AI was used for the PR description.")

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