feat: add topic hierarchy APIs

src/types/domain.ts

@@ -35,3 +35,10 @@ export interface FactTopicRecord {
   position: number;
   created_at: string;
 }
+
+export interface TopicRelationRecord {
+  parent_topic_id: string;
+  child_topic_id: string;
+  relation: string;
+  created_at: string;
+}