PluginConfig._load_resource() prepends self.__module__ (already
'netbox_rack_concept') to the configured path, so 'menu' and
'template_extensions' must be given relative to the plugin package
('navigation.menu', 'template_content.template_extensions'), not
prefixed with 'netbox_rack_concept.' again. The prefixed form made
Django try to import 'netbox_rack_concept.netbox_rack_concept...',
which doesn't exist, crashing manage.py on every command.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>