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>

e2e/settings.spec.ts

@@ -5,7 +5,7 @@ async function goToPolarisSettings(page: Page) {
   await page.goto('/c/main/settings/plugins');
 
   // Find and click the Polaris plugin entry to open its settings
-  const pluginEntry = page.locator('text=polaris').first();
+  const pluginEntry = page.locator('text=headlamp-polaris').first();
   await expect(pluginEntry).toBeVisible({ timeout: 15_000 });
   await pluginEntry.click();