feat: remove unused methods and improve widget styling in various screens

flutter/lib/core/ui/app_shell.dart

@@ -111,13 +111,6 @@ class AppShell extends ConsumerWidget {
         !location.startsWith('/recipes/');
     final isImportRoute = location == '/import';
 
-    Future<void> logout() async {
-      await ref.read(authStateProvider.notifier).logout();
-      if (context.mounted) {
-        context.go('/login');
-      }
-    }
-
     Widget shell = Scaffold(
       appBar: AppBar(
         title: Text(selectedDestination.title),

flutter/lib/core/ui/category_then_product_picker.dart

@@ -35,14 +35,6 @@ class CategoryThenProductPicker {
     }
     return ids;
   }
-
-  /// Hittar en nod med givet id djupet i trädet.
-  static AdminCategoryNode? _findNode(List<AdminCategoryNode> nodes, int id) {
-    for (final node in nodes) {
-      if (node.id == id) return node;
-      final found = _findNode(node.children, id);
-      if (found != null) return found;
-    }
     return null;
   }
 

flutter/lib/core/ui/product_picker_field.dart

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