feat: add infinite scroll to image list

[mikannkann]

Closes #177

[Copilot]

Pull Request Overview

This PR adds infinite scroll functionality to the ImageList component by implementing automatic loading when the "load more" button becomes visible in the viewport.

• Introduces IntersectionObserver-based automatic loading when the load more button is near the viewport
• Adds fallback logic to handle edge cases where content fits entirely within the viewport
• Maintains existing manual click functionality while adding seamless auto-loading behavior

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