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

lib/features/inventory/outbound/presentation/pages/outbound_page.dart

@@ -16,6 +16,13 @@ import 'package:superport_v2/features/inventory/shared/widgets/product_autocompl
 import 'package:superport_v2/features/inventory/shared/widgets/employee_autocomplete_field.dart';
 import 'package:superport_v2/features/inventory/shared/widgets/customer_multi_select_field.dart';
 import 'package:superport_v2/features/inventory/shared/widgets/warehouse_select_field.dart';
+import 'package:superport_v2/features/approvals/request/presentation/controllers/approval_request_controller.dart';
+import 'package:superport_v2/features/approvals/request/presentation/utils/approval_form_initializer.dart';
+import 'package:superport_v2/features/approvals/request/presentation/widgets/approval_step_configurator.dart';
+import 'package:superport_v2/features/approvals/request/presentation/widgets/approval_template_picker.dart';
+import 'package:superport_v2/features/approvals/domain/usecases/get_approval_draft_use_case.dart';
+import 'package:superport_v2/features/approvals/domain/usecases/list_approval_drafts_use_case.dart';
+import 'package:superport_v2/features/approvals/domain/usecases/save_approval_draft_use_case.dart';
 import 'package:superport_v2/core/config/environment.dart';
 import 'package:superport_v2/core/network/failure.dart';
 import 'package:superport_v2/core/common/utils/pagination_utils.dart';
@@ -31,6 +38,7 @@ import 'package:superport_v2/features/inventory/transactions/presentation/servic
 import 'package:superport_v2/features/inventory/transactions/presentation/widgets/transaction_detail_dialog.dart';
 import 'package:superport_v2/features/masters/customer/domain/entities/customer.dart';
 import 'package:superport_v2/features/masters/customer/domain/repositories/customer_repository.dart';
+import 'package:superport_v2/features/auth/application/auth_service.dart';
 import '../../../lookups/domain/entities/lookup_item.dart';
 import '../../../lookups/domain/repositories/inventory_lookup_repository.dart';
 import '../widgets/outbound_detail_view.dart';
@@ -133,6 +141,15 @@ class _OutboundPageState extends State<OutboundPage> {
       lookupRepository: getIt<InventoryLookupRepository>(),
       fallbackStatusOptions: OutboundTableSpec.fallbackStatusOptions,
       transactionTypeKeywords: OutboundTableSpec.transactionTypeKeywords,
+      saveDraftUseCase: getIt.isRegistered<SaveApprovalDraftUseCase>()
+          ? getIt<SaveApprovalDraftUseCase>()
+          : null,
+      getDraftUseCase: getIt.isRegistered<GetApprovalDraftUseCase>()
+          ? getIt<GetApprovalDraftUseCase>()
+          : null,
+      listDraftsUseCase: getIt.isRegistered<ListApprovalDraftsUseCase>()
+          ? getIt<ListApprovalDraftsUseCase>()
+          : null,
     );
   }
 
@@ -143,6 +160,10 @@ class _OutboundPageState extends State<OutboundPage> {
     }
     Future.microtask(() async {
       await controller.loadStatusOptions();
+      final requester = _resolveCurrentWriter();
+      if (requester != null) {
+        await controller.loadApprovalDraftFromServer(requesterId: requester.id);
+      }
       final hasType = await controller.resolveTransactionType();
       if (!mounted) {
         return;
@@ -213,6 +234,26 @@ class _OutboundPageState extends State<OutboundPage> {
     }
   }
 
+  InventoryEmployeeSuggestion? _resolveCurrentWriter() {
+    final getIt = GetIt.I;
+    if (!getIt.isRegistered<AuthService>()) {
+      return null;
+    }
+    final session = getIt<AuthService>().session;
+    final user = session?.user;
+    if (user == null) {
+      return null;
+    }
+    final employeeNo = (user.employeeNo ?? '').trim().isEmpty
+        ? user.id.toString()
+        : user.employeeNo!.trim();
+    return InventoryEmployeeSuggestion(
+      id: user.id,
+      employeeNo: employeeNo,
+      name: user.name,
+    );
+  }
+
   void _handleControllerChanged() {
     if (!mounted) {
       return;
@@ -1556,6 +1597,25 @@ class _OutboundPageState extends State<OutboundPage> {
       return '${suggestion.name} (${suggestion.employeeNo})';
     }
 
+    final approvalController = ApprovalRequestController();
+    final defaultRequester = () {
+      final writer = writerSelection;
+      if (writer == null) {
+        return null;
+      }
+      return ApprovalRequestParticipant(
+        id: writer.id,
+        name: writer.name,
+        employeeNo: writer.employeeNo,
+      );
+    }();
+    ApprovalFormInitializer.populate(
+      controller: approvalController,
+      existingApproval: initial?.raw?.approval,
+      draft: _controller?.approvalDraft,
+      defaultRequester: defaultRequester,
+    );
+
     final writerController = TextEditingController(
       text: writerLabel(writerSelection),
     );
@@ -1814,6 +1874,23 @@ class _OutboundPageState extends State<OutboundPage> {
             )
             .toList(growable: false);
 
+        StockTransactionApprovalInput approvalInput;
+        try {
+          approvalInput = approvalController.buildTransactionApprovalInput(
+            approvalStatusId: null,
+            note: approvalNoteValue.isEmpty ? null : approvalNoteValue,
+          );
+        } on StateError catch (error) {
+          updateSaving(false);
+          SuperportToast.error(context, error.message);
+          return;
+        } catch (_) {
+          updateSaving(false);
+          SuperportToast.error(context, '결재 구성을 확인하고 다시 시도하세요.');
+          return;
+        }
+        controller.updateApprovalDraft(approvalInput);
+
         final created = await controller.createTransaction(
           StockTransactionCreateInput(
             transactionTypeId: transactionTypeLookup.id,
@@ -1824,10 +1901,7 @@ class _OutboundPageState extends State<OutboundPage> {
             note: remarkValue,
             lines: createLines,
             customers: createCustomers,
-            approval: StockTransactionApprovalInput(
-              requestedById: createdById,
-              note: approvalNoteValue.isEmpty ? null : approvalNoteValue,
-            ),
+            approval: approvalInput,
           ),
         );
         result = created;
@@ -2011,6 +2085,15 @@ class _OutboundPageState extends State<OutboundPage> {
                           enabled: initial == null,
                           onSuggestionSelected: (suggestion) {
                             writerSelection = suggestion;
+                            approvalController.setRequester(
+                              suggestion == null
+                                  ? null
+                                  : ApprovalRequestParticipant(
+                                      id: suggestion.id,
+                                      name: suggestion.name,
+                                      employeeNo: suggestion.employeeNo,
+                                    ),
+                            );
                             if (writerError != null) {
                               setState(() {
                                 writerError = null;
@@ -2026,6 +2109,7 @@ class _OutboundPageState extends State<OutboundPage> {
                               if (currentText.isEmpty ||
                                   currentText != selectedLabel) {
                                 writerSelection = null;
+                                approvalController.setRequester(null);
                               }
                               if (writerError != null) {
                                 setState(() {
@@ -2099,6 +2183,15 @@ class _OutboundPageState extends State<OutboundPage> {
                     ),
                   ],
                 ),
+                const SizedBox(height: 16),
+                if (initial == null) ...[
+                  ApprovalTemplatePicker(controller: approvalController),
+                  const SizedBox(height: 16),
+                ],
+                ApprovalStepConfigurator(
+                  controller: approvalController,
+                  readOnly: initial != null,
+                ),
                 const SizedBox(height: 24),
                 if (headerNotice != null)
                   Padding(
@@ -2215,6 +2308,7 @@ class _OutboundPageState extends State<OutboundPage> {
     transactionTypeController.dispose();
     approvalNoteController.dispose();
     processedAt.dispose();
+    approvalController.dispose();
 
     return result;
   }