Sim Studio AI - Unauthenticated OAuth Token Theft

On SimStudio version below to 0.5.74, the `/api/auth/oauth/token` endpoint contains a code path that bypasses all authorization checks when provided with `credentialAccountUserId` and `providerId` parameters. An unauthenticated attacker can retrieve OAuth access tokens for any user by supplying their user ID and a provider name, effectively stealing credentials to third-party services.