feat: Add global disable toggle for --no-color and NO_COLOR

[kavix]

Description

Adds a global toggle to disable color output when --no-color or NO_COLOR environment variable is used. This suppresses ANSI escape codes across JSON, HTML, and header formats.

Fixes #11

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Added unit tests
• Tested via make test locally
• Compiled and tested via local binary (make build)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes