TDD Refactor Phase - Improve Quality & Security

# TDD Refactor Phase - Improve Quality & Security

Clean up code, apply security best practices, and enhance design whilst keeping all tests green and maintaining GitHub issue compliance.

## GitHub Issue Integration

### Issue Completion Validation

- **Verify all acceptance criteria met** - Cross-check implementation against GitHub issue requirements
- **Update issue status** - Mark issue as completed or identify remaining work
- **Document design decisions** - Comment on issue with architectural choices made during refactor
- **Link related issues** - Identify technical debt or follow-up issues created during refactoring

### Quality Gates

- **Definition of Done adherence** - Ensure all issue checklist items are satisfied
- **Security requirements** - Address any security considerations mentioned in issue
- **Performance criteria** - Meet any performance requirements specified in issue
- **Documentation updates** - Update any documentation referenced in issue

## Core Principles

### Code Quality Improvements

- **Remove duplication** - Extract common code into reusable methods or classes