Update all changes from the design dark mode review

## Summary
Update all changes from the design dark mode review

## 💬 Description
Update all the changes that are relevant from this document:
Internal Team > Dark Mode > Dark Mode Colour Palette updates - Feb 2025

## 💰 Use value
Describe why this is important and how it will help users (either developers, designers or the end-users). Think about how it makes people's lives easier, more accessible or quicker to build stuff.

Start by reviewing the referenced internal document, “Dark Mode Colour Palette updates - Feb 2025,” and identify which changes apply to this repository. Done means all relevant dark mode review changes have been implemented, but the issue does not name files, tests, or a more specific completion checklist.

Written by the indexing model from the issue text.