V131: metadata JSONB on phoenix_kit_staff_people.

Adds a general-purpose metadata JSONB NOT NULL DEFAULT '{}' column to the staff people table, mirroring the shape phoenix_kit_entities entity_data already uses. The immediate consumer is soft-delete: PhoenixKitStaff.Staff.trash_person/2 stashes the row's prior lifecycle status under metadata["trashed_from_status"] so restore_person/2 can return the person to active/inactive instead of unconditionally landing on "active".

The column is deliberately generic (not a trashed_from_status-specific field) so future per-person metadata can reuse it without another migration — same rationale as the entity_data metadata column.

Idempotent: ADD COLUMN IF NOT EXISTS, safe to re-run.