[BUG]: The unlocking button background is transparent - hard to see with custom theme/background image

[Extarys]

⚠️ This issue respects the following points: ⚠️

• [X] This is a single bug, not a question or a configuration/webserver/proxy issue.
• [X] This is not a bug in the browser extension or another client.
• [X] This issue is not already reported on Github (I've searched it).
• [X] Nextcloud Server and the Passwords App is up to date. See Nextcloud Apps.
• [X] There are no warnings and errors reported in the Passwords App settings in the admin area
• [X] The following apps are not installed: Rainloop

Server Information

Not revelent

Client Information

Browser and Version: Firefox 135 Client OS and Version: Rocky 9.5

Bug description

When using client-side encryption, the login page shows a password field and a button, but the button is not styled like the rest of Nextcloud UI. The background is transparent.

This is problematic when we use custom theme.

Steps to reproduce

1. Set a custom background in Admin > Theming
2. Set Password to use CSE and set a vault password
3. Try unlocking Password app

Expected behavior

1. The button should follow Nextcloud UI button style, or at least have an opaque background.

Nextcloud Logs

No response

Browser Logs

No response