chore(deps): pin Node 22.22+ for frontend builds

CodeRabbit on PR #49: the Docker build stages still used node:20-alpine,
which vite 7 (>=20.19/22.12) and react-router 8 (>=22.22) no longer
support. Bump NODE_VERSION to 22 in both Dockerfiles and declare
engines.node >=22.22.0 in both app manifests so local installs on an
old Node fail loudly instead of at build time.

DorkNet.Server/site/package.json

@@ -3,6 +3,9 @@
   "private": true,
   "version": "0.1.0",
   "type": "module",
+  "engines": {
+    "node": ">=22.22.0"
+  },
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",