feat(ai): enhance AI trace warnings and reason codes system

- Added structured warning system with `AdminAiWarning` type in backend and Flutter
- Implemented detailed reason descriptors with `FlyerReasonDescriptor` for parse and match operations
- Added `legacyWarnings` field to maintain backward compatibility
- Enhanced AI trace service to collect and format warnings with item-level context
- Updated flyer import services to include detailed reason descriptions in responses
- Added Swedish diacritic preservation for cheese variants (Prästost, Herrgårdsost, Grevéost)
- Implemented UTF-8 content validation for AI responses
- Added new reason code definitions in `reason-codes.ts`
- Updated Flutter UI to display structured warnings with severity indicators
- Added error report generation and copy functionality in admin panel
- Added comprehensive test coverage for new warning system and cheese normalization

BREAKING CHANGE: AI trace warnings are now structured objects instead of simple strings

flutter/lib/features/admin/presentation/admin_ai_panel.dart

@@ -137,6 +137,41 @@ class _AdminAiPanelState extends ConsumerState<AdminAiPanel> {
     return const JsonEncoder.withIndent('  ').convert(data);
   }
 
+  String _formatWarningLine(AdminAiWarning warning) {
+    final rowSuffix = warning.itemIndex == null ? '' : ' (rad ${warning.itemIndex})';
+    return '[${warning.severity}] ${warning.title}$rowSuffix: ${warning.message}';
+  }
+
+  String _buildErrorReport({
+    required AdminAiTraceDetail detail,
+    required String prettyOutput,
+  }) {
+    final warningCount = detail.warnings.length;
+    final buffer = StringBuffer()
+      ..writeln('[AI-trace ${detail.id}]')
+      ..writeln('Modell: ${detail.model ?? 'okänd'}')
+      ..writeln('Status: ${detail.status.name} ($warningCount varningar)')
+      ..writeln('Tid: ${detail.createdAt.toIso8601String()}')
+      ..writeln();
+
+    if (detail.warnings.isNotEmpty) {
+      buffer.writeln('Varningar:');
+      for (final warning in detail.warnings) {
+        buffer.writeln('- ${_formatWarningLine(warning)}');
+      }
+      buffer.writeln();
+    }
+
+    buffer
+      ..writeln('Prompt:')
+      ..writeln((detail.prompt ?? '').trim().isEmpty ? '[saknas]' : detail.prompt!.trim())
+      ..writeln()
+      ..writeln('Raw output:')
+      ..writeln((detail.rawOutput ?? '').trim().isEmpty ? prettyOutput : detail.rawOutput!.trim());
+
+    return buffer.toString().trimRight();
+  }
+
   Color _statusColor(AdminAiTraceStatus status, ColorScheme scheme) {
     return switch (status) {
       AdminAiTraceStatus.success => Colors.green.shade700,
@@ -348,16 +383,30 @@ class _AdminAiPanelState extends ConsumerState<AdminAiPanel> {
             ? const <String, dynamic>{}
             : {'rawOutput': detail.rawOutput});
     final prettyOutput = _prettyOutputFor(detail.id, outputJson);
+    final errorReport = _buildErrorReport(detail: detail, prettyOutput: prettyOutput);
 
     return ListView(
       children: [
         _TraceMetaCard(detail: detail, formatDateTime: _formatDateTime),
+        const SizedBox(height: 8),
+        Align(
+          alignment: Alignment.centerLeft,
+          child: OutlinedButton.icon(
+            onPressed: () => _copyText(errorReport, 'Felrapport'),
+            icon: const Icon(Icons.bug_report_outlined),
+            label: const Text('Kopiera felrapport'),
+          ),
+        ),
         if (detail.warnings.isNotEmpty) ...[
           const SizedBox(height: 12),
           _WarningsCard(
             warnings: detail.warnings,
-            onCopyWarning: (warning) => _copyText(warning, 'Varning'),
-            onCopyAll: () => _copyText(detail.warnings.join('\n'), 'Varningar'),
+            onCopyWarning: (warning) =>
+                _copyText(_formatWarningLine(warning), 'Varning'),
+            onCopyAll: () => _copyText(
+              detail.warnings.map(_formatWarningLine).join('\n'),
+              'Varningar',
+            ),
           ),
         ],
         const SizedBox(height: 12),
@@ -583,8 +632,8 @@ class _OutputJsonCardState extends State<_OutputJsonCard> {
 }
 
 class _WarningsCard extends StatelessWidget {
-  final List<String> warnings;
-  final void Function(String warning) onCopyWarning;
+  final List<AdminAiWarning> warnings;
+  final void Function(AdminAiWarning warning) onCopyWarning;
   final VoidCallback onCopyAll;
 
   const _WarningsCard({
@@ -622,8 +671,27 @@ class _WarningsCard extends StatelessWidget {
               (warning) => ListTile(
                 dense: true,
                 contentPadding: EdgeInsets.zero,
-                leading: const Icon(Icons.warning_amber_rounded, size: 18),
-                title: SelectableText(warning),
+                leading: Icon(_severityIcon(warning), size: 18, color: _severityColor(warning, theme)),
+                title: Text(
+                  warning.title,
+                  style: theme.textTheme.bodyMedium?.copyWith(fontWeight: FontWeight.w600),
+                ),
+                subtitle: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(warning.message),
+                    if ((warning.location ?? '').trim().isNotEmpty)
+                      Text(
+                        warning.location!,
+                        style: theme.textTheme.bodySmall,
+                      ),
+                    if (warning.itemIndex != null)
+                      Text(
+                        'Rad: ${warning.itemIndex}',
+                        style: theme.textTheme.bodySmall,
+                      ),
+                  ],
+                ),
                 trailing: IconButton(
                   tooltip: 'Kopiera varning',
                   onPressed: () => onCopyWarning(warning),
@@ -636,4 +704,26 @@ class _WarningsCard extends StatelessWidget {
       ),
     );
   }
+
+  IconData _severityIcon(AdminAiWarning warning) {
+    switch (warning.severity) {
+      case 'error':
+        return Icons.error_outline;
+      case 'warning':
+        return Icons.warning_amber_rounded;
+      default:
+        return Icons.info_outline;
+    }
+  }
+
+  Color _severityColor(AdminAiWarning warning, ThemeData theme) {
+    switch (warning.severity) {
+      case 'error':
+        return theme.colorScheme.error;
+      case 'warning':
+        return Colors.orange.shade700;
+      default:
+        return theme.colorScheme.primary;
+    }
+  }
 }