feat(flutter): 로그인 전에 받은 앱 링크를 로그인 뒤 이어서 연다

QR 을 기기 카메라로 찍어 앱이 열렸는데 로그인 전이면 인트로·로그인으로 가며 링크가 사라졌다.
링크를 기억해 두었다가 진입(인트로·로그인·온보딩)을 마치고 홈으로 갈 때 대신 연다.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

flutter/test/app_link_test.dart

@@ -1,9 +1,17 @@
 import 'dart:convert';
 
+import 'package:flutter/widgets.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:go_router/go_router.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:tma_app/app.dart';
+import 'package:tma_app/core/config/app_config.dart';
 import 'package:tma_app/core/config/app_links.dart';
+import 'package:tma_app/core/storage/preferences_provider.dart';
+import 'package:tma_app/features/auth/presentation/pages/login_page.dart';
 import 'package:tma_app/features/diary/domain/diary_invitation.dart';
+import 'package:tma_app/features/intro/presentation/pages/intro_page.dart';
 import 'package:tma_app/features/pet_card/data/received_card_repository.dart';
 import 'package:tma_app/features/pet_card/domain/card_style.dart';
 import 'package:tma_app/features/pet_card/domain/card_view_mode.dart';
@@ -168,4 +176,41 @@ void main() {
     expect(find.byType(ShareCalendarPage), findsOneWidget);
     expect(find.text('2/4'), findsOneWidget);
   });
+
+  testWidgets('로그인 전에 받은 링크는 기억했다가 로그인을 마치면 연다', (tester) async {
+    tester.view.physicalSize = const Size(402, 874);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    // 온보딩은 봤지만 로그인하지 않은 사람 — 인트로부터 시작한다
+    SharedPreferences.setMockInitialValues({'entry.onboardingSeen': true});
+    final prefs = await SharedPreferences.getInstance();
+    final cards = _CardRepo();
+    await tester.pumpWidget(ProviderScope(
+      overrides: [
+        sharedPreferencesProvider.overrideWithValue(prefs),
+        dataModeProvider.overrideWithValue(DataMode.local),
+        receivedCardRepositoryProvider.overrideWithValue(cards),
+      ],
+      child: const RupApp(),
+    ));
+    await tester.runAsync(() => Future<void>.delayed(const Duration(milliseconds: 300)));
+    await tester.pump(const Duration(seconds: 4));
+    await settle(tester);
+    expect(find.byType(IntroPage), findsOneWidget);
+
+    // 기기 카메라로 찍은 명함 링크 — 로그인 전이라 인트로에 머문다
+    await _openLink(tester, GoRouter.of(tester.element(find.byType(IntroPage))), petCardDeepLink('0428-117'));
+    expect(find.byType(IntroPage), findsOneWidget);
+    expect(cards.previewed, isEmpty);
+
+    await tester.tap(find.text('시작하기'));
+    await settle(tester);
+    expect(find.byType(LoginPage), findsOneWidget);
+    await tester.tap(find.text('카카오로 3초만에 시작하기'));
+    await settle(tester);
+    await settle(tester);
+
+    expect(cards.previewed, ['0428-117']);
+    expect(find.byType(ReceiveCardPage), findsOneWidget);
+  });
 }