feat: add UserRepository and CardRepository

src/main/java/com/example/bankcards/repository/CardRepository.java

@@ -0,0 +1,16 @@
+package com.example.bankcards.repository;
+
+import com.example.bankcards.entity.Card;
+import com.example.bankcards.entity.CardStatus;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface CardRepository extends JpaRepository<Card, Long> {
+    Page<Card> findByOwnerId(Long ownerId, Pageable pageable);
+    Page<Card> findByOwnerIdAndStatus(
+        Long ownerId,
+        CardStatus status,
+        Pageable pageable
+    );
+}

src/main/java/com/example/bankcards/repository/UserRepository.java

@@ -0,0 +1,11 @@
+package com.example.bankcards.repository;
+
+import com.example.bankcards.entity.User;
+import java.util.Optional;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface UserRepository extends JpaRepository<User, Long> {
+    Optional<User> findByUsername(String username);
+    boolean existsByUsername(String username);
+    boolean existsByEmail(String email);
+}