Threads serves actors at threads.net but their id field uses www.threads.net.
Extract apex_domain() helper and fall back to apex comparison when the
strict verify_domains_match check fails.
Person struct now deserializes gracefully when outbox, followers, or
following are absent (Threads omits them for some actors). Accepts
Service/Application/Organization/Group in addition to Person.
manually_approves_followers defaults to false when absent.
