chore(deps): bump vitest to 4.1.8 to clear critical audit finding

npm audit --audit-level=high (the Dependency Security Audit CI job) now
fails on a newly published critical advisory in vitest <4.1.0
(GHSA-5xrq-8626-4rwp: Vitest UI server can read/execute arbitrary files).
Bump vitest from ^4.0.18 to ^4.1.8. audit --audit-level=high exits 0; all
96 unit tests pass. Unblocks unrelated PRs whose CI this was failing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: raifdmueller

website/package-lock.json

@@ -34,7 +34,7 @@
     "prettier": "^3.8.1",
     "tailwindcss": "^4.2.1",
     "vite": "^7.3.1",
-    "vitest": "^4.0.18"
+    "vitest": "^4.1.8"
   },
   "dependencies": {
     "@asciidoctor/core": "^3.0.4",