- Stripe integration: add StripeService with checkout sessions, customer
portal, and webhook handling for subscription lifecycle events.
- Free trials: auto-start configurable trial on first subscription check,
with admin-controllable duration and enable/disable toggle.
- Cross-platform guard: prevent duplicate subscriptions across iOS, Android,
and Stripe by checking existing platform before allowing purchase.
- Subscription model: add Stripe fields (customer_id, subscription_id,
price_id), trial fields (trial_start, trial_end, trial_used), and
SubscriptionSource/IsTrialActive helpers.
- API: add trial and source fields to status response, update OpenAPI spec.
- Clean up stale migration and audit docs.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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