Redeem Invitation Code

Redeem a single-use invitation code for SDK tokens.

Public endpoint (no authentication required). Exchanges a valid, non-expired, single-use invitation code for access_token, refresh_token, and user_id. The returned token is write-only to the /sdk/* endpoints.

This backs the standalone onboarding flow used by the Open Wearables app and the SDK example apps. It is not the standard integration path - if your app has its own backend, mint and forward a token with POST /api/v1/users/{user_id}/token instead of redeeming codes on the client.