Component Change Request: use AAA contrast standards on Error notification bar

Please describe the change you wish to see

Aim for AAA WCAG color contrast standards on Errors notification bars

Please describe why these changes need to be made

The current Error notification styles pass normal AA contrast checks but fail AAA normal text check

In the case of Error notifications, it feels like we should go beyond normal requirements and make the text as easy to read as possible. Errors are already frustrating and it would compound user frustration to struggle to read the error description.

Please provide any designs or prototypes of the proposed changes

Enforcing large/bolded text might be the most effective solution.

Please describe where this component is currently in use

Screenshot above is from Newsletter error (locally forcing errors from the views.py file: http://localhost:8000/en-US/newsletter/confirm/thanks/?error=2)

Please describe what this component should do in the following conditions

• When set in front of a dark background
• When set in front of a light background
• When viewed in a mobile/responsive viewport

I don't think it needs any changes to responsive viewport behaviour or dark/light theme

Is the development of this component a blocking dependency for other work? Please explain if so

Not blocking

Start with the error variant of the notification-bar component documented at the linked Protocol page, then trace its SCSS implementation and the Newsletter error example described in the issue. Check the existing colors and typography against WCAG AAA normal-text contrast, and verify the result in light, dark, and responsive contexts. Done means the error notification meets the requested contrast standard without changing responsive or theme behavior.