feat: consolidate dashboard pages, fix namespace links, add tests

Merge Overview and Full Audit into a single dashboard page that always
shows the skipped check count. Fix namespace link 404s by using
Headlamp's Link component (which generates cluster-prefixed URLs)
instead of raw react-router-dom Link. Add vitest unit tests for all
polaris.ts utility functions.

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

package.json

@@ -10,7 +10,9 @@
     "lint": "eslint --ext .ts,.tsx src/",
     "lint:fix": "eslint --ext .ts,.tsx --fix src/",
     "format": "prettier --write src/",
-    "format:check": "prettier --check src/"
+    "format:check": "prettier --check src/",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "devDependencies": {
     "@kinvolk/headlamp-plugin": "^0.13.0"