Add draggable and collapsible panels to the UI layout

[tofarr]

This PR adds draggable and collapsible functionality to the panels in the UI layout:

• Added react-resizable-panels package
• Created a new CSS module for styling the resize handle
• Made the left panel (ChatInterface) resizable and collapsible
• Added visual feedback for the resize handle
• The left panel has a min size of 15% and max size of 50% of viewport width
• The right panel automatically adjusts its size as the left panel is resized

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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:55d4684-nikolaik   --name openhands-app-55d4684   docker.all-hands.dev/all-hands-ai/openhands:55d4684