fix: RecentActivity uses the wrong icons for each metric

[Nacho1499]

Closes #118

Summary of Changes:
This PR resolves issue #118 by updating the RecentActivity component to use semantically correct icons and dynamic coin data instead of hardcoded placeholders.

Details:

• Icon Mapping: Replaced incorrect icons ( call.svg and 50-50.svg) with users.svg for group size and participants, and coins.svg for earnings.
• Dynamic Data: Replaced the hardcoded trophy emoji (🏆) with activity.coins.gold and activity.coins.red.
• Accessibility: Added proper decorative alt text (alt="") to icons.
• Cleanup: Removed unused asset references from the component.

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