Add GitHub Actions workflows (KISS approach)

[josephwilson8-nhs]

Description:
Implement simple, essential GitHub Actions workflows following KISS principles.

Workflows to Add:

1. Testing - Run pytest on PRs and main branch
2. Linting - Run ruff check and format validation
3. Documentation - Build and deploy MkDocs site
4. Security - Gitleaks secret scanning

Tasks:

• Create .github/workflows/test.yml
• Create .github/workflows/lint.yml
• Create .github/workflows/docs.yml
• Create .github/workflows/gitleaks.yml
• Keep workflows simple and well-commented
• Add workflow status badges to README template

Acceptance Criteria:

• All workflows pass on template generation
• Workflows are easy to understand and modify
• No over-engineering - keep it simple
• Documentation explains each workflow

Priority: High
Type: Feature