[Bug]: Toolbar icons using the color that doesn't match the wallpaper

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When I use a third party wallpaper Nextcloud picks the wrong colors for icons in the toolbar.

Steps to reproduce

1. Go to Appearance and accessibility
2. Choose this wallpaper

Expected behavior

Toolbar icons are white while using a dark wallpaper.

Nextcloud Server version

30

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.1

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start by reproducing the issue through Appearance and accessibility with the reported third-party wallpaper. Trace how toolbar icon colors are selected for that wallpaper state, then verify that dark wallpapers produce white toolbar icons and add a regression check for the corrected behavior.