feat: add support for saving public key to file using -output flag

[pmpbaptista]

Description

• Introduced the -output flag to allow users to specify a file path for saving the public key.
• Updated the printPublicKey function to write the public key to the specified file, or to stdout if no file is provided.
• Modified the create and migrate cases to support the -output flag when printing the public key.
• Ensured backward compatibility by retaining stdout output when -output is not used.

Fixes # (issue)

Type of change

Please select all options that apply to this change:

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

Checklist:

Confirm you have completed the following steps:

• My code follows the style of this project.
• I have performed a self-review of my code.
• I have made corresponding updates to the documentation.
• I have added/updated unit tests to cover my changes.