Parallelize multi-year rank fetch (R7)

fetchRankFromKbo awaited each year's getOrFetch sequentially even though
years use independent cache keys. Map to Promise.all so multi-year lookups
run concurrently; order is preserved.

src/repositories/kboRepository.ts

@@ -43,15 +43,16 @@ const TTL_MS = 60 * 60 * 1000; // 1 hour
 export async function fetchRankFromKbo(
   years: number[]
 ): Promise<TeamRankResult[]> {
-  const results: TeamRankResult[] = [];
-  for (const year of years) {
+  // 연도별로 독립 캐시 키를 쓰므로 순차 대기할 이유가 없다. 병렬 처리해 다년도
+  // 조회 지연을 줄인다. Promise.all은 입력 순서를 보존한다.
+  return Promise.all(
+    years.map((year) => {
       const key = encodeKey(["rank", year]);
-    const result = await getOrFetch<TeamRankResult>(key, TTL_MS, () =>
+      return getOrFetch<TeamRankResult>(key, TTL_MS, () =>
         fetchSingleYearRank(year)
       );
-    results.push(result);
-  }
-  return results;
+    })
+  );
 }
 
 /**