Plans, Checkout, and account billing

Subscription purchase uses Stripe Checkout. Payment methods, invoices, and supported subscription changes use Stripe's Customer Portal. Card details do not pass through this application.

The application waits for verified Stripe events and displays the resulting local subscription projection. A browser return parameter never activates paid access by itself.

Active plan names, prices, intervals, features, and credit allowances come from the server-side Stripe mirror rather than hardcoded interface values.