feat(flyer-import): add session management and retrieval endpoints

- Add new API endpoints for retrieving flyer import sessions:
  - GET /flyer-import/sessions/latest - Retrieve latest session for user
  - GET /flyer-import/sessions/:sessionId - Retrieve specific session
- Implement session persistence and restoration in Flutter UI
- Add toJson() methods to FlyerImportItem and FlyerImportResult for serialization
- Add new FlyerImportSession domain model for local session management
- Add unit test file for FlyerImportService
- Update FlyerImportController with new endpoints and user ID extraction
- Update FlyerImportService with session retrieval logic and response mapping
- Update API paths in Flutter client
- Add session restoration on widget init in FlyerImportTab

flutter/lib/features/import/presentation/flyer_import_tab.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../../core/utils/pdf_opener.dart';
 import '../../auth/data/auth_providers.dart';
+import '../data/flyer_import_session.dart';
 import '../data/import_providers.dart';
 import '../domain/flyer_import_item.dart';
 import '../domain/flyer_import_result.dart';
@@ -23,6 +24,89 @@ class _FlyerImportTabState extends ConsumerState<FlyerImportTab> {
   FlyerImportResult? _result;
   final Map<int, bool> _selected = {};
 
+  @override
+  void initState() {
+    super.initState();
+    _restoreSession();
+  }
+
+  Future<void> _restoreSession() async {
+    final notifier = ref.read(flyerImportSessionProvider.notifier);
+    await notifier.restore();
+    var session = ref.read(flyerImportSessionProvider);
+
+    final token = await ref.read(authStateProvider.future);
+    final repo = ref.read(importRepositoryProvider);
+
+    if (session?.sessionId != null) {
+      try {
+        final serverResult = await repo.getFlyerImportSession(
+          sessionId: session!.sessionId!,
+          token: token,
+        );
+        if (!mounted) return;
+        final selected = session.selected.isEmpty
+            ? {
+                for (var i = 0; i < serverResult.items.length; i++)
+                  i: serverResult.items[i].matchedProductId != null,
+              }
+            : session.selected;
+        setState(() {
+          _result = serverResult;
+          _selected
+            ..clear()
+            ..addAll(selected);
+        });
+        notifier.setImportedResult(
+          result: serverResult,
+          selected: selected,
+          fileName: session.fileName,
+        );
+        return;
+      } catch (_) {
+        // fallback nedan
+      }
+    }
+
+    try {
+      final latest = await repo.getLatestFlyerImportSession(token: token);
+      if (!mounted) return;
+      if (latest.sessionId != null && latest.items.isNotEmpty) {
+        final selected = {
+          for (var i = 0; i < latest.items.length; i++)
+            i: latest.items[i].matchedProductId != null,
+        };
+        setState(() {
+          _result = latest;
+          _selected
+            ..clear()
+            ..addAll(selected);
+        });
+        notifier.setImportedResult(
+          result: latest,
+          selected: selected,
+          fileName: session?.fileName,
+        );
+      } else if (session?.result != null) {
+        setState(() {
+          _result = session!.result;
+          _selected
+            ..clear()
+            ..addAll(session.selected);
+        });
+      }
+    } catch (_) {
+      session = ref.read(flyerImportSessionProvider);
+      if (!mounted || session?.result == null) return;
+      setState(() {
+        _result = session!.result;
+        _selected
+          ..clear()
+          ..addAll(session.selected);
+      });
+    }
+  }
+
   Future<void> _pickFile() async {
     final result = await FilePicker.pickFiles(
       type: FileType.custom,
@@ -58,6 +142,11 @@ class _FlyerImportTabState extends ConsumerState<FlyerImportTab> {
           ..clear()
           ..addAll(selected);
       });
+      ref.read(flyerImportSessionProvider.notifier).setImportedResult(
+            result: parsed,
+            selected: selected,
+            fileName: file.name,
+          );
     } catch (e) {
       if (mounted) showErrorDialog(context, 'Flyerimport misslyckades: $e');
     } finally {
@@ -329,14 +418,15 @@ class _FlyerImportTabState extends ConsumerState<FlyerImportTab> {
                children: [
                  Text('${items.length} rader hittades', style: theme.textTheme.titleSmall),
                  TextButton(
-                   onPressed: () {
-                     final target = selectedCount < items.length;
-                     setState(() {
-                       for (var i = 0; i < items.length; i++) {
-                         _selected[i] = target;
-                       }
-                     });
-                   },
+                  onPressed: () {
+                    final target = selectedCount < items.length;
+                    setState(() {
+                      for (var i = 0; i < items.length; i++) {
+                        _selected[i] = target;
+                      }
+                    });
+                    ref.read(flyerImportSessionProvider.notifier).setSelectedForAll(items.length, target);
+                  },
                    child: Text(selectedCount < items.length ? 'Välj alla' : 'Avmarkera alla'),
                  ),
                ],
@@ -352,9 +442,13 @@ class _FlyerImportTabState extends ConsumerState<FlyerImportTab> {
                   ? ''
                   : _removeLimitTextFromOfferText(item.offerText!, limitText);
 
-               return CheckboxListTile(
-                 value: _selected[index] ?? false,
-                 onChanged: (value) => setState(() => _selected[index] = value ?? false),
+                return CheckboxListTile(
+                  value: _selected[index] ?? false,
+                  onChanged: (value) {
+                    final checked = value ?? false;
+                    setState(() => _selected[index] = checked);
+                    ref.read(flyerImportSessionProvider.notifier).setSelected(index, checked);
+                  },
                  title: Row(
                    children: [
                      Expanded(child: Text(item.rawName)),