Merge branch 's-morimto' of https://gitea.it-college.co.jp/2026_09_5H_Spring_KIZAKI/Monegement into k-kobayashi

src/main/java/com/example/demo/app/infra/repository/UserRepository.java

@@ -16,5 +16,6 @@ public interface UserRepository extends JpaRepository<UserEntity, Long> {
             String mailAddress,
             String password);
 
+    Optional<UserEntity> findByMailAddress(String mailAddress);
 }