Stripe ⇄ Discord
Server läuft.
- POST /create-checkout-session {"priceId":"price_..."} (optional mit ?survey=1&token=...)
- /success?session_id=... führt zur Discord-Verknüpfung
- n8n Endpoints: POST /internal/discord/grant | /internal/discord/revoke
- Stripe Webhook: POST /webhooks/stripe