feat: API 인증 시스템 구현 및 로그인 화면 연동

- AuthService, AuthRemoteDataSource 구현
- JWT 토큰 관리 (SecureStorage 사용)
- 로그인 화면 API 연동 및 에러 처리
- freezed 패키지로 Auth 관련 DTO 모델 생성
- 의존성 주입 설정 업데이트

lib/data/datasources/remote/auth_remote_datasource.dart

@@ -0,0 +1,104 @@
+import 'package:dartz/dartz.dart';
+import 'package:injectable/injectable.dart';
+import 'package:superport/core/errors/exceptions.dart';
+import 'package:superport/core/errors/failures.dart';
+import 'package:superport/data/datasources/remote/api_client.dart';
+import 'package:superport/data/models/auth/login_request.dart';
+import 'package:superport/data/models/auth/login_response.dart';
+import 'package:superport/data/models/auth/logout_request.dart';
+import 'package:superport/data/models/auth/refresh_token_request.dart';
+import 'package:superport/data/models/auth/token_response.dart';
+
+abstract class AuthRemoteDataSource {
+  Future<Either<Failure, LoginResponse>> login(LoginRequest request);
+  Future<Either<Failure, void>> logout(LogoutRequest request);
+  Future<Either<Failure, TokenResponse>> refreshToken(RefreshTokenRequest request);
+}
+
+@LazySingleton(as: AuthRemoteDataSource)
+class AuthRemoteDataSourceImpl implements AuthRemoteDataSource {
+  final ApiClient _apiClient;
+
+  AuthRemoteDataSourceImpl(this._apiClient);
+
+  @override
+  Future<Either<Failure, LoginResponse>> login(LoginRequest request) async {
+    try {
+      final response = await _apiClient.post(
+        '/auth/login',
+        data: request.toJson(),
+      );
+
+      if (response.success && response.data != null) {
+        final loginResponse = LoginResponse.fromJson(response.data);
+        return Right(loginResponse);
+      } else {
+        return Left(ServerFailure(
+          message: response.error?.message ?? '로그인 실패',
+        ));
+      }
+    } catch (e) {
+      if (e is ApiException) {
+        if (e.statusCode == 401) {
+          return Left(AuthenticationFailure(
+            message: '이메일 또는 비밀번호가 올바르지 않습니다.',
+          ));
+        }
+        return Left(ServerFailure(message: e.message));
+      }
+      return Left(ServerFailure(message: '로그인 중 오류가 발생했습니다.'));
+    }
+  }
+
+  @override
+  Future<Either<Failure, void>> logout(LogoutRequest request) async {
+    try {
+      final response = await _apiClient.post(
+        '/auth/logout',
+        data: request.toJson(),
+      );
+
+      if (response.success) {
+        return const Right(null);
+      } else {
+        return Left(ServerFailure(
+          message: response.error?.message ?? '로그아웃 실패',
+        ));
+      }
+    } catch (e) {
+      if (e is ApiException) {
+        return Left(ServerFailure(message: e.message));
+      }
+      return Left(ServerFailure(message: '로그아웃 중 오류가 발생했습니다.'));
+    }
+  }
+
+  @override
+  Future<Either<Failure, TokenResponse>> refreshToken(RefreshTokenRequest request) async {
+    try {
+      final response = await _apiClient.post(
+        '/auth/refresh',
+        data: request.toJson(),
+      );
+
+      if (response.success && response.data != null) {
+        final tokenResponse = TokenResponse.fromJson(response.data);
+        return Right(tokenResponse);
+      } else {
+        return Left(ServerFailure(
+          message: response.error?.message ?? '토큰 갱신 실패',
+        ));
+      }
+    } catch (e) {
+      if (e is ApiException) {
+        if (e.statusCode == 401) {
+          return Left(AuthenticationFailure(
+            message: '인증이 만료되었습니다. 다시 로그인해주세요.',
+          ));
+        }
+        return Left(ServerFailure(message: e.message));
+      }
+      return Left(ServerFailure(message: '토큰 갱신 중 오류가 발생했습니다.'));
+    }
+  }
+}