feat: Implement admin pantry item management with create and update functionality, including category selection and validation

flutter/lib/features/admin/domain/admin_pantry_item.dart

@@ -6,6 +6,8 @@ class AdminPantryItem {
   final int productId;
   final String productName;
   final String? productCanonicalName;
+  final int? categoryId;
+  final String? categoryPath;
   final String? location;
 
   const AdminPantryItem({
@@ -16,6 +18,8 @@ class AdminPantryItem {
     required this.productId,
     required this.productName,
     this.productCanonicalName,
+    this.categoryId,
+    this.categoryPath,
     this.location,
   });
 
@@ -28,6 +32,15 @@ class AdminPantryItem {
   factory AdminPantryItem.fromJson(Map<String, dynamic> json) {
     final user = (json['user'] as Map<String, dynamic>?) ?? const {};
     final product = (json['product'] as Map<String, dynamic>?) ?? const {};
+    final names = <String>[];
+    dynamic current = product['categoryRef'];
+    while (current is Map<String, dynamic>) {
+      final name = current['name']?.toString().trim();
+      if (name != null && name.isNotEmpty) {
+        names.insert(0, name);
+      }
+      current = current['parent'];
+    }
     return AdminPantryItem(
       id: (json['id'] as num).toInt(),
       userId: (json['userId'] as num).toInt(),
@@ -36,6 +49,8 @@ class AdminPantryItem {
       productId: (json['productId'] as num).toInt(),
       productName: product['name'] as String? ?? '',
       productCanonicalName: product['canonicalName'] as String?,
+      categoryId: (product['categoryId'] as num?)?.toInt(),
+      categoryPath: names.isEmpty ? null : names.join(' > '),
       location: json['location'] as String?,
     );
   }