Support company-only client contacts in scheduler (no required last name)

Users are asking to add company-only client support in the scheduling flow, so they can enter a business name without being forced to provide a person-style last name.

Today, the scheduler requires first and last name for the primary contact, which leads teams to use placeholder values (for example, a period) when onboarding company clients. Users want a clean, intentional option for company-as-client scenarios while still allowing person-based contacts where needed.

Why it matters: This removes data workarounds, improves data quality, and makes onboarding business clients more consistent for client care teams.