사이드바 메뉴 숨김: 우편번호 검색·재고 이력 항목 비노출 처리

- SidebarMenu에 기능 토글(static const) 추가
- 우편번호 검색(Routes.zipcode), 재고 이력(Routes.inventoryHistory) 메뉴를 조건부 렌더링으로 숨김
- 라우트/코드는 유지하며 메뉴에서만 비노출

lib/screens/common/app_layout.dart

@@ -1008,6 +1008,10 @@ class SidebarMenu extends StatelessWidget {
     required this.expiringMaintenanceCount,
   });
 
+  // Feature visibility toggles for sidebar (hide without removing routes)
+  static const bool _enableInventoryMenu = false; // 재고관리(재고 이력) 메뉴 숨김
+  static const bool _enableZipcodeMenu = false;   // 우편번호 검색 메뉴 숨김
+
   @override
   Widget build(BuildContext context) {
     return Column(
@@ -1067,16 +1071,17 @@ class SidebarMenu extends StatelessWidget {
                   badge: null,
                 ),
 
-                _buildMenuItem(
-                  icon: Icons.history,
-                  title: '재고 이력',
-                  route: Routes.inventoryHistory,
-                  isActive: [
-                    Routes.inventory,
-                    Routes.inventoryHistory,
-                  ].contains(currentRoute),
-                  badge: null,
-                ),
+                if (_enableInventoryMenu)
+                  _buildMenuItem(
+                    icon: Icons.history,
+                    title: '재고 이력',
+                    route: Routes.inventoryHistory,
+                    isActive: [
+                      Routes.inventory,
+                      Routes.inventoryHistory,
+                    ].contains(currentRoute),
+                    badge: null,
+                  ),
 
                 _buildMenuItem(
                   icon: Icons.warehouse_outlined,
@@ -1086,13 +1091,14 @@ class SidebarMenu extends StatelessWidget {
                   badge: null,
                 ),
 
-                _buildMenuItem(
-                  icon: Icons.location_on_outlined,
-                  title: '우편번호 검색',
-                  route: Routes.zipcode,
-                  isActive: currentRoute == Routes.zipcode,
-                  badge: null,
-                ),
+                if (_enableZipcodeMenu)
+                  _buildMenuItem(
+                    icon: Icons.location_on_outlined,
+                    title: '우편번호 검색',
+                    route: Routes.zipcode,
+                    isActive: currentRoute == Routes.zipcode,
+                    badge: null,
+                  ),
 
                 _buildMenuItem(
                   icon: Icons.business_outlined,