rsvp_announcement: department community terms (not a field)

Decision (ADR-0022 update): no separate field_department on announcement. Departments ARE rsvp_community terms with community_type = "department". field_community_owner points directly to the department term. Action: populate rsvp_community terms for ~30 Whitingham departments: - Selectboard, Town Clerk, Library, Animal Control, etc. - Each gets community_type = "department" (already exists in rsvp_community_type) - field_short_name = machine-safe slug (e.g. selectboard, town-clerk, library) URL pattern resolves automatically: department/selectboard/announcements/[title] Note: "department" community_type term already exists in rsvp_community_type_terms defaults (uuid: e716e6e9-d7ba-4584-b645-32a115f18ee9).