Fix useScrollToBottom hook for rapid content changes

[tofarr]

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• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

End-user friendly description of the problem this fixes or functionality that this introduces.
This PR fixes an issue with the useScrollToBottom hook when content changes rapidly. The current implementation sometimes fails to maintain the scroll position at the bottom when new content is added quickly.

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Give a summary of what the PR does, explaining any non-trivial design decisions.

Changes

• Improved scroll behavior logic to better track when the user is at the bottom of the scroll area
• Added smooth scrolling with fast animation for better user experience
• Created a CSS class for consistent scroll behavior across components
• Applied optimizations to all components using the scroll hook (chat interface, jupyter, invariant)

Testing

• All existing tests pass
• Manually verified that the scroll position stays at the bottom when content changes rapidly
• Verified that the user can still scroll up to view previous content and the auto-scroll will only resume when they scroll back to the bottom

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Link of any specific issues this addresses.

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:d6da053-nikolaik   --name openhands-app-d6da053   docker.all-hands.dev/all-hands-ai/openhands:d6da053