Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/site/src/pages/NotFound.tsx

@@ -0,0 +1,11 @@
+import { Link } from 'react-router-dom';
+
+export function NotFound() {
+  return (
+    <div className="card !p-8 text-center">
+      <h2 className="text-xl font-semibold text-ink-50">Page not found</h2>
+      <p className="text-sm text-ink-400 mt-1">The page you were looking for doesn't exist on this server.</p>
+      <Link to="/" className="btn-primary text-sm mt-4 inline-flex">Go home</Link>
+    </div>
+  );
+}