UX: Show a loading indicator when downloading a zip

[tofarr]

Show a Loading indicator when downloading a zip

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

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Currently, downloading a zip is a silent operation. This shows a working indicator when a zip file is downloading

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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:23087ab-nikolaik   --name openhands-app-23087ab   docker.all-hands.dev/all-hands-ai/openhands:23087ab

[amanape]

Why is it set twice?

[tofarr]

For success and error

[neubig]

Thank you, I'm happy to have this improvement!
Just a note that this fixes #4615