Allow sending messages while client is connecting

[xingyaoww]

Description

This PR implements a feature that allows users to send messages while the OpenHands client is still connecting. Messages are queued and automatically sent once the connection is established.

Changes

• Added message queuing system in WebSocket client provider
• Updated UI to show pending message count
• Modified input disabling logic to allow message input during loading
• Enhanced status indicators to provide better feedback

Benefits

• Improved user experience by allowing immediate interaction
• Reduced perceived latency
• Better feedback about connection status
• Seamless transition when connection is established

Fixes the issue where users see "Waiting for client to become ready..." and cannot interact with the chat interface.

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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:d5a996a-nikolaik   --name openhands-app-d5a996a   docker.all-hands.dev/all-hands-ai/openhands:d5a996a