refactor(curd): optimize relation binding and code generation

- Move relation binding logic from model constructor to controller
- Generate controller code for binding select fields-Remove unnecessary code and templates
- Improve code readability and maintainability

app/admin/service/curd/templates/controller/controller.code

@@ -20,6 +20,7 @@ class {{controllerName}} extends AdminController
         parent::__construct($app);
         $this->model = new {{modelFilename}}();
         $this->notes = $notes = $this->model->notes;
+        {{constructRelation}}
         $this->assign(compact('notes'));
     }