docs: Add repository Code of Conduct based on Contributor Covenant v2.1

[ayushsri-dev]

Description

This PR introduces an official CODE_OF_CONDUCT.md file to establish community behavior standards, pledge commitments, scope, enforcement responsibilities, and a 4-tier enforcement ladder (Correction, Warning, Temporary Ban, Permanent Ban) for the Arvio ecosystem.

The document adopts the industry-standard Contributor Covenant Version 2.1 to ensure a welcoming, inclusive, and harassment-free environment for all contributors, maintainers, and community members participating in issues, pull requests, and repository discussions.

Summary of Changes

• Created CODE_OF_CONDUCT.md at the repository root based on Contributor Covenant v2.1.
• Established community pledge, acceptable/unacceptable behavior examples, maintainer responsibilities, and scope.
• Included the Community Impact Enforcement Guidelines (Correction, Warning, Temporary Ban, Permanent Ban).
• Added standard attribution links to Contributor Covenant v2.1 and the Mozilla Diversity Enforcement Ladder.

Maintainer Note / Action Required

The Enforcement section currently references "project maintainers responsible for enforcement". Prior to merging, maintainers may optionally update the contact details with a dedicated private reporting email address (e.g., conduct@arvio.tv or a maintainer email).

PR Checklist

• Documentation follows repository formatting and Markdown standards.
• Changes do not contain hardcoded API keys, private credentials, or copyrighted media URLs.
• Upstream Contributor Covenant v2.1 attribution and license terms are preserved.
• Scope is strictly limited to community governance documentation (CODE_OF_CONDUCT.md).

Closes #480