refactor: rename npm package to headlamp-polaris-plugin

Aligns npm package name with the repo and ArtifactHub package name.
Updates all references: package.json, registerPluginSettings, Dockerfile,
release workflow tarball URLs, artifacthub-pkg.yml archive-url, and README.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/index.tsx

@@ -44,4 +44,4 @@ registerRoute({
   ),
 });
 
-registerPluginSettings('polaris-headlamp-plugin', PolarisSettings, true);
+registerPluginSettings('headlamp-polaris-plugin', PolarisSettings, true);