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>

package-lock.json

@@ -1,11 +1,11 @@
 {
-  "name": "polaris-headlamp-plugin",
+  "name": "headlamp-polaris-plugin",
   "version": "0.0.8",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
-      "name": "polaris-headlamp-plugin",
+      "name": "headlamp-polaris-plugin",
       "version": "0.0.8",
       "devDependencies": {
         "@kinvolk/headlamp-plugin": "^0.13.0"