feat: UserRepository 추가

Author: MEOHIN

src/main/java/com/back/domain/user/repository/UserRepository.java

@@ -0,0 +1,10 @@
+package com.back.domain.user.repository;
+
+import com.back.domain.user.entity.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface UserRepository extends JpaRepository<User, Long> {
+}
+