One more SecretStr fix

[tofarr]

JWT Secret Type Fix

• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

Improved security by properly handling JWT secrets using Pydantic SecretStr type.

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Give a summary of what the PR does, explaining any non-trivial design decisions

This PR fixes the handling of JWT secrets by properly wrapping them in Pydantic's SecretStr type. The changes include:

1. Added SecretStr import from pydantic
2. Modified the jwt_secret assignment in finalize_config to wrap the secret in SecretStr

This change ensures that sensitive JWT secrets are properly handled and not accidentally exposed in logs or string representations.

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Link of any specific issues this addresses

N/A - Security improvement

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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:227e292-nikolaik   --name openhands-app-227e292   docker.all-hands.dev/all-hands-ai/openhands:227e292

[malhotra5]

LGTM