fix: improve theming and settings visibility

- Fix namespace detail panel to follow system dark/light theme
- Use proper CSS custom properties for background and text colors
- Fix plugin settings registration (remove deprecated third parameter)
- Ensure close button and headers respect theme colors
- Version bump to 0.2.5

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via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "headlamp-polaris-plugin",
-  "version": "0.2.4",
+  "version": "0.2.5",
   "description": "Headlamp plugin for Fairwinds Polaris audit results",
   "scripts": {
     "start": "headlamp-plugin start",