feat(approvals): Approval Flow v2 프런트엔드 전면 개편

- 환경/라우터 모듈에 approval_flow_v2 토글을 추가하고 FeatureFlags 초기화를 연결 (.env*, lib/core/**)
- ApiClient 빌더·ApiRoutes 확장과 ApprovalRepositoryRemote 리팩터링으로 include·액션 시그니처를 정합화
- ApprovalFlow·ApprovalDraft 엔티티/레포/유즈케이스를 도입해 서버 초안과 단계 액션(승인·회수·재상신)을 지원
- Approval 컨트롤러·히스토리·템플릿 페이지와 공유 위젯을 재작성해 감사 로그·회수 UX·템플릿 CRUD를 반영
- Inbound/Outbound/Rental 컨트롤러·페이지에 결재 섹션을 삽입하고 대시보드 pending 카드 요약을 갱신
- SuperportDialog·FormField 등 공통 위젯을 보강하고 승인 위젯 가이드를 추가해 UI 가이드를 정리
- 결재/재고 테스트 픽스처와 단위·위젯·통합 테스트를 확장하고 flutter_test_config로 스테이징 호스트를 허용
- Approval Flow 레포트/플랜 문서를 업데이트하고 ApprovalFlow_System_Integration_and_ChangePlan.md를 추가
- 실행: flutter analyze, flutter test

test/features/approvals/template/presentation/pages/approval_template_page_test.dart

@@ -7,12 +7,17 @@ import 'package:shadcn_ui/shadcn_ui.dart';
 
 import 'package:superport_v2/core/common/models/paginated_result.dart';
 import 'package:superport_v2/features/approvals/domain/entities/approval_template.dart';
+import 'package:superport_v2/features/approvals/domain/repositories/approval_repository.dart';
 import 'package:superport_v2/features/approvals/domain/repositories/approval_template_repository.dart';
+import 'package:superport_v2/features/approvals/domain/usecases/apply_approval_template_use_case.dart';
+import 'package:superport_v2/features/approvals/domain/usecases/save_approval_template_use_case.dart';
 import 'package:superport_v2/features/approvals/template/presentation/pages/approval_template_page.dart';
 
 class _MockApprovalTemplateRepository extends Mock
     implements ApprovalTemplateRepository {}
 
+class _MockApprovalRepository extends Mock implements ApprovalRepository {}
+
 class _FakeTemplateInput extends Fake implements ApprovalTemplateInput {}
 
 class _FakeTemplateStepInput extends Fake
@@ -56,13 +61,27 @@ void main() {
 
   group('플래그 On', () {
     late _MockApprovalTemplateRepository repository;
+    late _MockApprovalRepository approvalRepository;
 
     setUp(() {
       dotenv.testLoad(fileInput: 'FEATURE_APPROVALS_ENABLED=true\n');
       repository = _MockApprovalTemplateRepository();
+      approvalRepository = _MockApprovalRepository();
       GetIt.I.registerLazySingleton<ApprovalTemplateRepository>(
         () => repository,
       );
+      GetIt.I.registerLazySingleton<ApprovalRepository>(
+        () => approvalRepository,
+      );
+      GetIt.I.registerLazySingleton<SaveApprovalTemplateUseCase>(
+        () => SaveApprovalTemplateUseCase(repository: repository),
+      );
+      GetIt.I.registerLazySingleton<ApplyApprovalTemplateUseCase>(
+        () => ApplyApprovalTemplateUseCase(
+          templateRepository: repository,
+          approvalRepository: approvalRepository,
+        ),
+      );
     });
 
     ApprovalTemplate buildTemplate({bool isActive = true}) {
@@ -114,6 +133,7 @@ void main() {
 
       expect(find.text('AP_INBOUND'), findsOneWidget);
       expect(find.text('입고 템플릿'), findsOneWidget);
+      expect(find.textContaining('1. 최승인'), findsOneWidget);
 
       verify(
         () =>
@@ -188,6 +208,54 @@ void main() {
       expect(find.text('템플릿 "신규 템플릿"을 생성했습니다.'), findsOneWidget);
     });
 
+    testWidgets('보기 버튼을 눌러 템플릿 단계를 미리본다', (tester) async {
+      final template = buildTemplate();
+
+      when(
+        () => repository.list(
+          page: any(named: 'page'),
+          pageSize: any(named: 'pageSize'),
+          query: any(named: 'query'),
+          isActive: any(named: 'isActive'),
+        ),
+      ).thenAnswer(
+        (_) async => PaginatedResult<ApprovalTemplate>(
+          items: [template],
+          page: 1,
+          pageSize: 20,
+          total: 1,
+        ),
+      );
+
+      when(
+        () => repository.fetchDetail(template.id, includeSteps: true),
+      ).thenAnswer((_) async => template);
+
+      await tester.pumpWidget(_buildApp(const ApprovalTemplatePage()));
+      await tester.pump();
+      await tester.pumpAndSettle();
+
+      final previewFinder = find.text('보기', skipOffstage: false);
+
+      await tester.dragUntilVisible(
+        previewFinder,
+        find.text(template.name),
+        const Offset(-200, 0),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.tap(previewFinder);
+      await tester.pump();
+      await tester.pumpAndSettle();
+
+      expect(find.text(template.name), findsWidgets);
+      expect(find.textContaining('사번 E001'), findsOneWidget);
+
+      verify(
+        () => repository.fetchDetail(template.id, includeSteps: true),
+      ).called(1);
+    });
+
     testWidgets('수정 플로우에서 fetchDetail 후 update를 호출한다', (tester) async {
       final activeTemplate = buildTemplate();