List focus candidate attributes

Focus candidate attributes are the subset of a job's job_candidate_attributes that an individual interview kit elevates as focus areas — the attributes Greenhouse highlights at the top of the interviewer's scorecard so they know which traits to prioritize for that interview. The set is per interview kit, so the same job_candidate_attribute can appear as a focus attribute on multiple kits within the same job. Each row carries only the foreign keys — the attribute's display name and candidate_attribute_type come from the parent job_candidate_attribute. Filter by interview_kit_ids to retrieve a single kit's focus attributes, or by job_candidate_attribute_ids to find every interview kit that focuses on a given attribute. Today this endpoint is site-admin-only.