Enhance task status for FAILURE with error and traceback

[Amit-Matth]

Description

This PR enhances the task status reporting for FAILURE states. Previously, the API only returned a simple exception message. This change introduces a TaskError model and updates the status field to include both the error message and the full traceback.

This enhancement aligns the API with the improvements in the RSTUF Worker (repository-service-tuf-worker #190) and provides better diagnostic information for developers.

Ref: repository-service-tuf/repository-service-tuf-worker#190
Closes: #249

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)

Additional requirements

• Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

Code of Conduct

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• I agree to follow this project's Code of Conduct

[kairoaraujo]

@Amit-Matth,
Help me here, would it break existent users task handler clients parsing the response?
I mean, you marked as New feature (non-breaking change which adds functionality)

[Amit-Matth]

@kairoaraujo, thanks for catching that. I initially marked this as a "New feature" because it adds diagnostic details for failures, but since it changes the status type from boolean to an object, it is indeed a Breaking change. I've updated the PR type to reflect this. This implementation follows the enhancement requested in #190. Clients previously checking for False should now check for the presence of the error key.