feat: color contrasts in default theme

[JammingBen]

Description

Enhances colors in the default theme so they have at least a 4.5:1 contrast ratio because of a11y reasons.

Note that checking out this PR will not change the colors since those are only being used as fallback if no theme was provided by oCIS. https://github.com/owncloud/ocis/pull/9752 is for the actual theme change in oCIS.

Notable changes:

• reduced the opacity in a few spots, e.g. the file extensions in the "New"-menu, a cut resource
• reduced the brightness of the secondary background color in dark mode
• redefined colors for the danger button in dark mode (see "Empty trash bin"-button)
• removed hover effect on disabled menu actions

Related Issue

• Works towards https://github.com/owncloud/web/issues/10726

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Technical debt
• [ ] Tests
• [ ] Documentation
• [ ] Maintenance (e.g. dependency updates or tooling)

[update-docs[bot]]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
10 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[JammingBen]

is the contrast of the danger button in dark mode & validation error text color supposed to be fixed? (currently, contrasts are not high enough)

Yes, as described above, checking out this PR will not display the changes. It's just the fallback theme if oCIS fails to deliver a theme. So you either need to run oCIS with https://github.com/owncloud/ocis/pull/9752, or mount the theme in the docker container via a volume: - ./packages/web-runtime/themes/owncloud/theme.json:/themes/owncloud/theme.json