Add CODE_OF_CONDUCT.md

[czarekk215]

Feature: Add Code of Conduct

Description

Add a Code of Conduct to the repository to clearly define acceptable behavior,
promote a respectful and inclusive environment, and set expectations for contributors
and collaborators.

Motivation

As the project grows, having a Code of Conduct helps:

• establish clear community standards
• improve communication and collaboration
• protect contributors and maintainers
• align the project with common open-source best practices

Acceptance Criteria

• A CODE_OF_CONDUCT.md file is added to the root of the repository
• The document is based on a well-known standard (e.g. Contributor Covenant or PSF Code of Conduct)
• Contact or reporting information is clearly provided
• The Code of Conduct is referenced in the README.md (if applicable)

Additional Notes

This change does not affect application logic and is purely a documentation
and community standard improvement.