feat(ai): enhance AI trace warnings with product context

- Added `productName` field to `AdminAiWarning` to include product context in warnings
- Updated `collectWarnings` to extract and include `rawName` as `productName` in AI trace warnings
- Added `signals` field to `FlyerParseItem` type for detailed product signals
- Enhanced Flutter admin panel to display product names in AI trace warnings
- Added new `AdminAiTraceResponse` DTO for AI trace data structure

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

@@ -8,6 +8,7 @@ class AdminAiWarning {
   final String severity;
   final String? location;
   final int? itemIndex;
+  final String? productName;
 
   const AdminAiWarning({
     required this.code,
@@ -17,6 +18,7 @@ class AdminAiWarning {
     required this.severity,
     required this.location,
     required this.itemIndex,
+    required this.productName,
   });
 
   factory AdminAiWarning.fromJson(Map<String, dynamic> json) {
@@ -28,6 +30,7 @@ class AdminAiWarning {
       severity: (json['severity'] ?? '').toString(),
       location: json['location']?.toString(),
       itemIndex: (json['itemIndex'] as num?)?.toInt(),
+      productName: json['productName']?.toString(),
     );
   }
 
@@ -44,6 +47,7 @@ class AdminAiWarning {
       severity: 'warning',
       location: null,
       itemIndex: null,
+      productName: null,
     );
   }
 }