Review alanube-python compatibility with updated API error format and documentation

[wilmerm]

The Alanube API changelog announces improvements to the documentation and a unified error response format.

This issue tracks the review of alanube-python to ensure it complies with these changes and continues to behave correctly.

Scope:

• Verify that all API error responses handled by the library match the new unified error format.
• Check that error parsing, exceptions, and messages are consistent across endpoints.
• Validate that recent documentation changes do not introduce breaking changes for current implementations.
• Add or update tests covering the standardized error responses, if missing.

Reference:

• https://developer.alanube.co/changelog/api-fe-dom-mejora-de-la-documentaci%C3%B3n-y-unificaci%C3%B3n-del-formato-de-errores.md

Acceptance criteria:

• No regressions in existing functionality.
• Errors are parsed and exposed consistently.
• Tests pass and cover the updated behavior.