refactor(frontend): migration of use-optimistic-user-message.ts to zustand

[hieptl]

• This change is worth documenting at https://docs.all-hands.dev/
• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

End-user friendly description of the problem this fixes or functionality this introduces.

Task Overview:

• The use-optimistic-user-message.ts file must be migrated to use Zustand for state management.

Acceptance Criteria:

• The use-optimistic-user-message.ts file is successfully refactored to utilize Zustand.
• All existing functionality remains intact, with no regressions or broken features.

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Summarize what the PR does, explaining any non-trivial design decisions.

The PR updates the code to migrate use-optimistic-user-message.ts to Zustand.

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Link of any specific issues this addresses:

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To run this PR locally, use the following command:

GUI with Docker:

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:9803342-nikolaik   --name openhands-app-9803342   docker.all-hands.dev/all-hands-ai/openhands:9803342

CLI with uvx:

uvx --python 3.12 --from git+https://github.com/All-Hands-AI/OpenHands@hieptl/all-3670 openhands

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • Run Python Tests

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #11148 at branch `hieptl/all-3670`

Feel free to include any additional details that might help me get this PR into a better state.

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[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.