fix: unknown user accent fallback [WPB-24378]

[Garzas]

https://wearezeta.atlassian.net/browse/WPB-24378

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• The PR Title

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What's new in this PR?

Issues

Users who never selected an accent color, for example users who only used Web or iOS, could be shown with the current Android user's accent color in bubble message author styling.

Causes (Optional)

For users without an explicit accent color, Android receives or stores the accent as Accent.Unknown / accentId = 0. In bubble message author styling, Accent.Unknown fell back to the current theme primary color, which is based on the logged-in user's selected accent.

Solutions

Use the default Wire Blue accent for Accent.Unknown in bubble message author styling, while preserving the existing non-bubble fallback behavior. Also render name-based avatars with the default accent color mapping so unknown accents resolve consistently in light and dark mode.

[sonarqubecloud]

Quality Gate passed

Issues
0 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 SonarQube Cloud