feat(receipt-import): add refresh categories endpoint and UI integration

Co-authored-by: Copilot <copilot@github.com>

flutter/lib/core/api/api_paths.dart

@@ -25,6 +25,10 @@ class CategoryApiPaths {
   static const tree = '/categories/tree';
 }
 
+class ReceiptImportApiPaths {
+  static const refreshCategories = '/receipt-import/refresh-categories';
+}
+
 class RecipeApiPaths {
   static const list = '/recipes';
   static String detail(int id) => '/recipes/$id';