the finances skeleton — repo, prefix and permission key, before any feature

Published empty on purpose: identity is the expensive part to change later, the
feature is the cheap part to add. One route, two placeholder panels, no tables and
no sidecar.

web/FinancesDetail.tsx

@@ -0,0 +1,15 @@
+import { useParams } from "react-router";
+
+// The second panel, reading the section from the URL rather than from the panel beside it.
+export const FinancesDetail = () => {
+  const { section } = useParams();
+
+  return (
+    <div className="h-full overflow-auto p-6">
+      <h2 className="text-lg font-semibold text-duck-dark">Detail</h2>
+      <p className="mt-1 text-sm text-duck-dark/60">
+        Section from the URL: <code>{section ?? "(none)"}</code>
+      </p>
+    </div>
+  );
+};