feat(flyer-import): add detailed product signals and display names

- Added `signals` and `displayNameDetailed` fields to FlyerItem model in Prisma schema
- Introduced `FlyerImportSignals` type with origin countries, labels, quality flags, variant, and packaging
- Added `displayNameDetailed` field to FlyerImportItem DTO and Flutter model
- Implemented utility functions for signal extraction and display name building
- Updated flyer import service to persist and return signals/category data
- Enhanced Flutter UI to display detailed product information including badges for signals
- Added new test coverage for signals persistence and display name generation
- Added new import-common module for shared import utilities
- Created database migration for new fields
- Added Kilo plan for feature development

flutter/test/features/import/domain/flyer_import_item_test.dart

@@ -0,0 +1,29 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:recipe_flutter/features/import/domain/flyer_import_item.dart';
+
+void main() {
+  test('parses signals and detailed bundle name', () {
+    final item = FlyerImportItem.fromJson({
+      'flyerItemId': 7,
+      'rawName': 'Kaptenens Favoriter',
+      'displayNameDetailed':
+          'Kaptenens Favoriter (Chumlax 3x100g + Alaska pollock 3x100g)',
+      'normalizedName': 'kaptenens favoriter',
+      'isBundle': true,
+      'bundleItems': ['Chumlax 3x100g', 'Alaska pollock 3x100g'],
+      'signals': {
+        'originCountries': ['Sverige'],
+        'labels': ['Ekologisk'],
+        'qualityFlags': ['eco'],
+        'variant': null,
+        'packaging': 'multipack',
+      },
+    });
+
+    expect(item.isBundle, isTrue);
+    expect(item.displayNameDetailed, contains('Chumlax 3x100g'));
+    expect(item.bundleItems, hasLength(2));
+    expect(item.signals?.originCountries, ['Sverige']);
+    expect(item.toJson()['signals'], isA<Map<String, dynamic>>());
+  });
+}