feat: RankingEntry 클래스 추가

Author: rnqhstmd

apps/commerce-api/src/main/java/com/loopers/domain/ranking/RankingEntry.java

@@ -0,0 +1,7 @@
+package com.loopers.domain.ranking;
+
+public record RankingEntry(
+        Long productId,
+        Double score
+) {
+}