feat: always save log file on error

[MarcelRosier]

Addressing #139

[Copilot]

Pull request overview

Adds automatic temporary log-file creation to inference runs and ensures the log is preserved when inference fails, improving debuggability without requiring users to explicitly pass a log_file.

Changes:

• InferenceSetup now always attaches a log file handler; when log_file is not provided it creates a temporary brats_*.log, deletes it on success, and preserves it (printing its path to stderr) on error.
• Adds/updates unit tests to verify temp-log cleanup on success and preservation on failure.
• Improves container error visibility by printing container output to stderr and updating the raised exception message.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
tests/utils/test_data_handling.py	Adds tests asserting temp-log cleanup on success and preservation on error.
brats/utils/data_handling.py	Implements automatic temp-log creation and conditional cleanup/preservation in InferenceSetup.
brats/core/docker.py	Prints container failure output to stderr and updates the exception guidance message.

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[PaulaTBz]

this feature exactly tackles the problem of the related issue and provides robust logging that requires no action from the user, which makes it very convenient in the case of failure and greatly improves logging