Move Redis polling to dedicated thread

[rbren]

This PR moves the Redis polling loop from the asyncio event loop to a dedicated thread, which should improve performance by not blocking the event loop.

Changes:

• Add threading module and thread control event
• Replace asyncio task with daemon thread for Redis polling
• Use asyncio.run_coroutine_threadsafe for message processing from thread
• Improve error handling and cleanup

The Redis polling now runs in its own thread while maintaining thread safety by scheduling message processing in the asyncio event loop.

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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:3c3fbd6-nikolaik   --name openhands-app-3c3fbd6   docker.all-hands.dev/all-hands-ai/openhands:3c3fbd6