feat: enhance product picker and improve error handling in inventory screen

flutter/lib/core/ui/product_picker_field.dart

@@ -11,6 +11,8 @@ typedef ProductOption = ({int id, String name});
 /// Replaces a long [DropdownButtonFormField] when the product list is large.
 /// Works both inside and outside a [Form].
 class ProductPickerField extends StatelessWidget {
+  static const _clearSelectionToken = '__clear_selection__';
+
   final List<ProductOption> products;
 
   /// Currently selected product id, or null if nothing is selected.
@@ -51,7 +53,7 @@ class ProductPickerField extends StatelessWidget {
               orElse: () => null,
             );
 
-    final interactive = enabled && !isLoading;
+    final interactive = enabled && !isLoading && products.isNotEmpty;
 
     return MouseRegion(
       cursor: interactive ? SystemMouseCursors.click : MouseCursor.defer,
@@ -73,7 +75,11 @@ class ProductPickerField extends StatelessWidget {
                   ),
                 )
               : selected == null
-                  ? const Icon(Icons.search)
+                  ? Text(
+                      products.isEmpty
+                          ? 'Inga produkter tillgängliga'
+                          : 'Tryck för att välja produkt',
+                    )
                   : Text(selected.name),
         ),
       ),
@@ -81,7 +87,7 @@ class ProductPickerField extends StatelessWidget {
   }
 
   Future<void> _openPicker(BuildContext context) async {
-    final selectedId = await showModalBottomSheet<int?>(
+    final result = await showModalBottomSheet<Object?>(
       context: context,
       isScrollControlled: true,
       useSafeArea: true,
@@ -114,7 +120,8 @@ class ProductPickerField extends StatelessWidget {
                           ),
                         ),
                         TextButton.icon(
-                          onPressed: () => Navigator.pop(context, null),
+                          onPressed: () =>
+                              Navigator.pop(context, _clearSelectionToken),
                           icon: const Icon(Icons.clear),
                           label: const Text('Rensa'),
                         ),
@@ -169,10 +176,15 @@ class ProductPickerField extends StatelessWidget {
     );
 
     if (!context.mounted) return;
-    if (selectedId == null) {
+    if (result == null) {
+      return;
+    }
+    if (result == _clearSelectionToken) {
       onChanged?.call(null);
       return;
     }
-    onChanged?.call(selectedId);
+    if (result is int) {
+      onChanged?.call(result);
+    }
   }
 }

flutter/lib/features/inventory/presentation/create_inventory_screen.dart

@@ -57,16 +57,26 @@ class _CreateInventoryScreenState
       final token = await ref.read(authStateProvider.future);
       final api = ref.read(apiClientProvider);
       final data = await api.getJson(ProductApiPaths.list, token: token);
+      final list = data is List<dynamic>
+          ? data
+          : (data is Map<String, dynamic> && data['items'] is List<dynamic>)
+              ? data['items'] as List<dynamic>
+              : const <dynamic>[];
       if (mounted) {
         setState(() {
-          _products = (data as List<dynamic>)
+          _products = list
               .map((e) => e as Map<String, dynamic>)
               .toList();
           _loadingProducts = false;
         });
       }
-    } catch (_) {
+    } catch (e) {
       if (mounted) setState(() => _loadingProducts = false);
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(mapErrorToUserMessage(e, context))),
+        );
+      }
     }
   }
 
@@ -147,7 +157,7 @@ class _CreateInventoryScreenState
     final productOptions = sortedProducts
         .map(
           (p) => (
-            id: p['id'] as int,
+            id: (p['id'] as num).toInt(),
             name: (p['canonicalName'] ?? p['name'] ?? '').toString(),
           ),
         )