test: verify Docker image builds and starts successfully with custom port

[icebear0828]

This PR resolves issue #120 by adding a workflow job step to .github/workflows/ci-docker.yml that:

1. Creates a custom configuration mapping port: 8090.
2. Starts the docker container with the custom default.yaml config volume mounted.
3. Tests the port 8090 container for health up to 30s.
4. Cleans up gracefully upon completion.

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PR created automatically by Jules for task 9105682765508942711 started by @icebear0828

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