feat: Improve subscription workflow

[eulixir]

Describe your changes

Backend – subscription lifecycle

• Handle Stripe webhooks: customer.subscription.deleted, customer.subscription.updated; only run completeSubscription when checkout.session.completed is for subscription mode.
• Add provider_subscription_id and subscription_provider to subscriptions; store Stripe subscription ID on completion and use it in webhooks and cancel/schedule flows.
• Introduce SubscriptionProvider port and Stripe adapter; make cancel/schedule services depend on the port for provider calls.
• Idempotent cancel: treat “already canceled” from provider as success and sync DB; add SubscriptionAlreadyCanceledError and webhook signature verification via STRIPE_WEBHOOK_SECRET.
• Migration: add subscription_provider with DEFAULT 'STRIPE' so existing rows migrate without NOT NULL errors.
• Backend – API
• DELETE /user/subscription with body { when: 'now' | 'at_end_of_current_period', reason? }; subscriptions route registered with app.after + withTypeProvider and operationId: 'deleteSubscription' for Swagger/orval.

Frontend

• Subscription tab in user settings: show plan (Free/PRO), cancel subscription with “Cancel now” and “At end of period” via deleteSubscription; use dictionary for all copy and fix hydration (no

  wrapping Badge).

• Add generate:api script in web app for orval.

Issue ticket number and link

Checklist before requesting a review

• I have performed a self-review of my code
• If it's an essential feature, I've tested it thoroughly.
• Do we need to implement analytics?
• Will this be part of a product update? If yes, please write one phrase about this update.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
plotwist	Error		Feb 2, 2026 2:31pm