feat: enhance ProductPickerField and ParsedReceiptItem to support category filtering in receipt import

flutter/lib/core/ui/product_picker_field.dart

@@ -4,7 +4,7 @@ import 'package:flutter/material.dart';
 typedef ValueChanged<T> = void Function(T value);
 
 /// A named record representing a selectable product option.
-typedef ProductOption = ({int id, String name});
+typedef ProductOption = ({int id, String name, int? categoryId});
 
 /// A form field that opens a searchable bottom sheet for selecting a product.
 ///
@@ -110,19 +110,28 @@ class ProductPickerField extends StatelessWidget {
 
   /// Öppnar produktväljarens bottenark utan att binda den till en specifik widget-instans.
   /// Returnerar valt produkt-id, null (ingen ändring), eller [_clearSelectionToken] (rensa).
+  ///
+  /// [categoryFilter] — om satt visas bara produkter vars categoryId finns i listan.
+  /// Används med AI-kategorisuggestion för att förifiltrera på rätt kategorigren.
   static Future<int?> showSheet(
     BuildContext context, {
     required List<ProductOption> products,
     int? value,
     String label = 'Produkt',
     String? initialQuery,
+    Set<int>? categoryFilter,
   }) async {
+    // Filtrera på kategori om angiven, men visa alla om filtret ger nollresultat
+    final baseList = categoryFilter != null && categoryFilter.isNotEmpty
+        ? products.where((p) => p.categoryId != null && categoryFilter.contains(p.categoryId)).toList()
+        : products;
+    final useList = baseList.isNotEmpty ? baseList : products;
+
     final result = await showModalBottomSheet<Object?>(
       context: context,
       isScrollControlled: true,
       useSafeArea: true,
       builder: (sheetContext) {
-        // Skapa controller EN gång per öppnad ark — inte inuti StatefulBuilder
         final controller = TextEditingController(text: initialQuery ?? '');
         var query = initialQuery ?? '';
 
@@ -130,11 +139,13 @@ class ProductPickerField extends StatelessWidget {
           builder: (ctx, setModalState) {
             final normalizedQuery = query.trim().toLowerCase();
             final filtered = normalizedQuery.isEmpty
-                ? products
-                : products
+                ? useList
+                : useList
                     .where((p) => p.name.toLowerCase().contains(normalizedQuery))
                     .toList();
 
+            final isFiltered = useList.length < products.length;
+
             return SizedBox(
               height: MediaQuery.of(ctx).size.height * 0.85,
               child: Column(
@@ -144,7 +155,17 @@ class ProductPickerField extends StatelessWidget {
                     child: Row(
                       children: [
                         Expanded(
-                          child: Text(label, style: Theme.of(ctx).textTheme.titleMedium),
+                          child: Column(
+                            crossAxisAlignment: CrossAxisAlignment.start,
+                            children: [
+                              Text(label, style: Theme.of(ctx).textTheme.titleMedium),
+                              if (isFiltered)
+                                Text(
+                                  'Visar ${useList.length} produkter i föreslagen kategori',
+                                  style: Theme.of(ctx).textTheme.labelSmall?.copyWith(color: Colors.green.shade700),
+                                ),
+                            ],
+                          ),
                         ),
                         TextButton.icon(
                           onPressed: () => Navigator.pop(ctx, _clearSelectionToken),