- Add get_tier_by_code and get_tier_id helper methods
- Update get_or_create_subscription to set tier_id
- Update create_subscription to set tier_id
- Update update_subscription to sync tier_id when tier changes
- Update upgrade_tier to set tier_id
All subscription CRUD operations now maintain the tier_id FK relationship
in sync with the tier code string.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>