chore: bump version to 0.3.9

Fixes drawer transparency by using --mui-palette-background-default
which is fully opaque and follows Headlamp's theme system.

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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": "polaris",
-  "version": "0.3.8",
+  "version": "0.3.9",
   "description": "Headlamp plugin for Fairwinds Polaris audit results",
   "repository": {
     "type": "git",