[56343] Move Colours page into a tab of Admin/Design page

[bsatarnejad]

Ticket

https://community.openproject.org/projects/openproject/work_packages/56343/activity

What are you trying to accomplish?

We want to remove admin/colors page and move its content to a separate tab in admin/design page.

Screenshots

What approach did you choose and why?

Merge checklist

• [ ] Added/updated tests
• [ ] Added/updated documentation in Lookbook (patterns, previews, etc)
• [ ] Tested major browsers (Chrome, Firefox, Edge, ...)