How v0 authenticates to Snowflake without exposing the user's OAuth token

Introduced a Snowflake request proxy for v0 sandboxes, built on the Vercel Sandbox firewall, to securely authenticate AI-generated applications to Snowflake. This proxy resolves user credentials server-side and injects them only into designated authentication fields within requests, preventing exposure of user OAuth tokens to untrusted code. The solution handles different Snowflake authentication flows (SQL API, login requests) and implements a 'fail closed' security model to reject requests with potential credential misuse.