Implement Configuration Diffing

[Carrington-dev]

Description

Add ability to compare configurations between environments.

Tasks

• Create diff algorithm for configurations
• Add visual diff output
• Support comparing files
• Support comparing environments
• Add JSON/YAML diff output
• Add HTML diff report
• Create CLI command for diffing
• Add API for programmatic diffing
• Write documentation

Acceptance Criteria

• Diffs accurate and useful
• Multiple output formats supported
• Easy to use from CLI
• Helpful for debugging