fix block footer in gin darkmode

Problem/Motivation

In the new "Drupal Events" block on the dashboard, the dark mode styling for the Gin theme (or when using dark mode preferences) is inconsistent. Specifically, the .events-feed and .events-cta sections use a hardcoded or incorrectly mapped variable var(--color-gray-025) for the background. This results in a very bright background (#F9FAFF) that breaks the dark mode aesthetic and reduces readability.

Steps to reproduce

• Enable Dark Mode on the Drupal.org dashboard.
• Scroll to the "Drupal Events" block.
• Observe the background color of the events feed and the CTA area; it remains light/white despite the rest of the UI being dark.

Proposed resolution

Update the CSS for the events block to use a theme-appropriate background variable or a specific dark mode override. Overwriting the background with a darker tone (e.g., #222) resolves the issue and integrates better with the Dark Mode UI.

Remaining tasks

• Identify the exact CSS file providing the .events-feed styling.
• Apply a media query for (prefers-color-scheme: dark) or update the Gin-specific color mapping.
• Verify the fix across different viewport sizes.

User interface changes

The "Drupal Events" block will now correctly display a dark background when Dark Mode is active, ensuring a consistent user experience.

API changes

None.

Data model changes

None.