feat(frontend): enhance GitHub repo picker with search and sorting

[rbren]

This PR enhances the GitHub repository picker with the following features:

• Add GitHub API search for public repos when user enters a query
• Show stargazer count for searched repos
• Keep repos sorted by pushed_at (most recent first)
• Place searched repo at the top of the picker

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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:89adac2-nikolaik   --name openhands-app-89adac2   docker.all-hands.dev/all-hands-ai/openhands:89adac2