feat: clean up imports and fix minor formatting issues in various files

flutter/lib/core/ui/app_shell.dart

@@ -1,6 +1,5 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
-import 'package:go_router/go_router.dart';
 
 import '../../features/auth/data/auth_providers.dart';
 import '../../features/recipes/data/recipes_grid_provider.dart';

flutter/lib/core/ui/category_then_product_picker.dart

@@ -35,8 +35,6 @@ class CategoryThenProductPicker {
     }
     return ids;
   }
-    return null;
-  }
 
   /// Öppnar ett bottenark med kategoriträdet. Klick på en lövnod (inga barn)
   /// öppnar direkt produktpickern för den kategorin.

flutter/lib/core/ui/product_picker_field.dart

@@ -105,8 +105,7 @@ class ProductPickerField extends StatelessWidget {
       onChanged?.call(null);
       return;
     }
-    if (result is! int) return;
-    onChanged?.call(result);
+    onChanged?.call(result as int);
   }
 
   /// Öppnar produktväljarens bottenark utan att binda den till en specifik widget-instans.

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

@@ -987,7 +987,7 @@ class _ReceiptImportResultRow extends ConsumerWidget {
                 Icon(Icons.kitchen_outlined, size: 12, color: Colors.blue.shade700),
                 const SizedBox(width: 3),
                 Text(
-                  'I lager: ${existingInv.quantity} ${existingInv.unit} → blir ${(existingInv.quantity + convertedPreviewQty!).toStringAsFixed(existingInv.quantity % 1 == 0 ? 0 : 2)} ${existingInv.unit}',
+                  'I lager: ${existingInv.quantity} ${existingInv.unit} → blir ${(existingInv.quantity + convertedPreviewQty).toStringAsFixed(existingInv.quantity % 1 == 0 ? 0 : 2)} ${existingInv.unit}',
                   style: theme.textTheme.bodySmall?.copyWith(color: Colors.blue.shade700),
                 ),
               ]),

flutter/lib/features/profile/presentation/user_aliases_screen.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../admin/data/admin_repository.dart';
-import '../../admin/domain/receipt_alias.dart';}
+import '../../admin/domain/receipt_alias.dart';
 
 class UserAliasesScreen extends ConsumerStatefulWidget {
   const UserAliasesScreen({super.key});