chore: finish frontend ESLint migration #18

Enable every plugin recommended preset and replace Biome with ESLint formatting.

Preserve API contracts and JSX whitespace; verify source, tests, builds and tooling.

src/app/routes/ProtectedLayout.tsx

@@ -1,5 +1,7 @@
 import type { FC } from "react";
+
 import { AppBreadcrumbs, AppShell } from "@/app/ui";
+
 import { ProtectedDocumentTitle } from "./DocumentTitle/DocumentTitle";
 
 const ProtectedLayout: FC = () => {