- Add subscription module (models, service, tests)
- Plans: Free, Creator ($9.99/mo), Premium ($19.99/mo)
- Features: subscribe, cancel, reactivate, change billing cycle
- 14-day trial for Premium plan
- Upgrade immediate, downgrade at period end
- Invoice tracking and history
- Handler tests for auth and validation
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
