Improve alt text in building-community

[edent]

Added longer descriptions so that alt text users can understand the more complex images.

Avatar images have empty alt text because they are decorative.

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[Copilot]

Pull Request Overview

This PR improves accessibility for screen reader users by enhancing alt text descriptions for complex images and properly marking avatar images as decorative.

• Enhanced alt text descriptions for complex images to provide meaningful context for screen reader users
• Changed avatar images to have empty alt text as they are decorative elements
• Improved accessibility compliance by providing descriptive text for informational images

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