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/transactions/data/dtos/stock_transaction_dto.dart

@@ -1,5 +1,6 @@
 import 'package:superport_v2/core/common/models/paginated_result.dart';
 import 'package:superport_v2/core/common/utils/json_utils.dart';
+import 'package:superport_v2/features/approvals/data/dtos/approval_dto.dart';
 
 import '../../domain/entities/stock_transaction.dart';
 
@@ -38,7 +39,7 @@ class StockTransactionDto {
   final DateTime? updatedAt;
   final List<StockTransactionLine> lines;
   final List<StockTransactionCustomer> customers;
-  final StockTransactionApprovalSummary? approval;
+  final ApprovalDto? approval;
   final DateTime? expectedReturnDate;
 
   /// JSON 객체를 DTO로 변환한다.
@@ -86,7 +87,7 @@ class StockTransactionDto {
       updatedAt: updatedAt,
       lines: lines,
       customers: customers,
-      approval: approval,
+      approval: approval?.toEntity(),
       expectedReturnDate: expectedReturnDate,
     );
   }
@@ -328,43 +329,21 @@ StockTransactionCustomerSummary _parseCustomer(
   );
 }
 
-StockTransactionApprovalSummary? _parseApproval(dynamic raw) {
+ApprovalDto? _parseApproval(dynamic raw) {
   final map = _mapOrEmpty(raw);
   if (map.isEmpty) {
     return null;
   }
-  final statusMap = _firstNonEmptyMap([map['approval_status'], map['status']]);
-  return StockTransactionApprovalSummary(
-    id: map['id'] as int? ?? 0,
-    approvalNo:
-        map['approval_no'] as String? ?? map['approvalNo'] as String? ?? '',
-    status: statusMap.isEmpty
-        ? null
-        : StockTransactionApprovalStatusSummary(
-            id: statusMap['id'] as int? ?? statusMap['status_id'] as int? ?? 0,
-            name:
-                statusMap['name'] as String? ??
-                statusMap['status_name'] as String? ??
-                '-',
-            isBlocking:
-                statusMap['is_blocking_next'] as bool? ??
-                statusMap['isBlocking'] as bool?,
-          ),
-  );
+  try {
+    return ApprovalDto.fromJson(map);
+  } catch (_) {
+    return null;
+  }
 }
 
 Map<String, dynamic> _mapOrEmpty(dynamic value) =>
     value is Map<String, dynamic> ? value : const <String, dynamic>{};
 
-Map<String, dynamic> _firstNonEmptyMap(List<dynamic> candidates) {
-  for (final candidate in candidates) {
-    if (candidate is Map<String, dynamic> && candidate.isNotEmpty) {
-      return candidate;
-    }
-  }
-  return const <String, dynamic>{};
-}
-
 int _readQuantity(Object? value) {
   if (value is int) {
     return value;