refactor(db): name audit entity_type constants for vocab/term/authority (#21)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/db/src/authority.rs

@@ -8,6 +8,8 @@ use sqlx::Row;
 
 use crate::audit;
 
+const AUTHORITY_ENTITY_TYPE: &str = "authority";
+
 /// Labels aggregated per row as JSON, to read an authority and its labels in one query.
 const LABELS_JSON: &str = "COALESCE(json_agg(json_build_object('lang', al.lang, 'label', al.label) \
      ORDER BY al.lang) FILTER (WHERE al.authority_id IS NOT NULL), '[]'::json)";
@@ -43,7 +45,7 @@ pub async fn create_authority(
         &NewAuditEvent {
             actor,
             action: AuditAction::Created,
-            entity_type: "authority".to_owned(),
+            entity_type: AUTHORITY_ENTITY_TYPE.to_owned(),
             entity_id: id.to_uuid(),
             changes: Vec::new(),
         },