CVE-2026-48709: OliveTin: ValidateArgumentType API Endpoint's Missing Authentication Allows Action and Argument Enumeration

The ValidateArgumentType RPC endpoint in service/internal/api/api.go does not perform any authentication or authorization checks. Unlike all other data-returning API endpoints, it does not call auth.UserFromApiCall or checkDashboardAccess. When AuthRequireGuestsToLogin is enabled (the security-conscious configuration), this endpoint remains accessible to unauthenticated users and can be used as an oracle to enumerate valid action binding IDs and their argument configurations.