refactor: Remove PantryProduct class and simplify category resolution in PantryScreen

flutter/lib/features/pantry/domain/pantry_item.dart

@@ -5,6 +5,7 @@ class PantryItem {
   final String? canonicalName;
   final String? category;
   final int? categoryId;
+  final String? categoryPath;
   final String? location;
 
   const PantryItem({
@@ -14,6 +15,7 @@ class PantryItem {
     this.canonicalName,
     this.category,
     this.categoryId,
+    this.categoryPath,
     this.location,
   });
 
@@ -24,6 +26,17 @@ class PantryItem {
     return productName;
   }
 
+  String? get l1CategoryOrNull {
+    final path = categoryPath?.trim();
+    if (path != null && path.isNotEmpty) {
+      return path.split('>').first.trim();
+    }
+    if (category != null && category!.trim().isNotEmpty) {
+      return category!.trim();
+    }
+    return null;
+  }
+
   factory PantryItem.fromJson(Map<String, dynamic> json) {
     final product = json['product'] as Map<String, dynamic>? ?? {};
     return PantryItem(
@@ -33,7 +46,25 @@ class PantryItem {
       canonicalName: product['canonicalName']?.toString(),
       category: product['category']?.toString(),
       categoryId: (product['categoryId'] as num?)?.toInt(),
+      categoryPath: _buildCategoryPath(product['categoryRef']),
       location: json['location']?.toString(),
     );
   }
+
+  static String? _buildCategoryPath(dynamic rawCategoryRef) {
+    if (rawCategoryRef is! Map<String, dynamic>) return null;
+
+    final names = <String>[];
+    dynamic current = rawCategoryRef;
+    while (current is Map<String, dynamic>) {
+      final name = current['name']?.toString().trim();
+      if (name != null && name.isNotEmpty) {
+        names.add(name);
+      }
+      current = current['parent'];
+    }
+
+    if (names.isEmpty) return null;
+    return names.reversed.join(' > ');
+  }
 }