fix: align registerPluginSettings and E2E test with package.json name

Headlamp identifies plugins by reading package.json from the plugin
directory. Since package.json name is 'headlamp-polaris', both the
registerPluginSettings call and the E2E settings test must use
'headlamp-polaris', not 'polaris'.

- registerPluginSettings('polaris') → registerPluginSettings('headlamp-polaris')
- E2E test locator: text=polaris → text=headlamp-polaris

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/index.tsx

@@ -99,7 +99,7 @@ registerRoute({
 });
 
 // Register plugin settings
-registerPluginSettings('polaris', PolarisSettings, true);
+registerPluginSettings('headlamp-polaris', PolarisSettings, true);
 
 // Register details view section for supported controller types
 registerDetailsViewSection(({ resource }) => {