Returns all tenants the authenticated user has access to.

GET https://{tenant}.rubixx.app/api/v3/users/me/licenses

Requires a Bearer token only — no tenant-specific API key. This endpoint is intentionally
tenant-agnostic so callers can discover which tenants they belong to before they know
which subdomain to target. It is callable from any valid tenant subdomain regardless of
whether the authenticated user holds a license for that subdomain. The Customer/Member
policies are deliberately not applied — tenant-specific UserType claims are not available
when the caller has no LinkUser in the resolved tenant.