fix(career): public CV deep links work on direct load, refresh, and shared links

Phase 4.5 (priority 4). The app is a React Router SPA behind Next static
export, which only generated `/` — so a hard load of any deep path (/cv/{slug},
/login, /career/builder/…) hit Next's client not-found before React Router
could route it. Replace the single app/page.tsx with an optional catch-all
app/[[...slug]] (server page + client shell so generateStaticParams stays
server-only) that matches every path; nginx already serves index.html for
unknown paths (try_files), so React Router now owns routing on direct load.

Also: PublicCvPage shows a friendly 404 empty state and sets the document
title. Verified live — /login and /cv/{slug} both resolve on direct navigation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

job-tracker-ui/app/[[...slug]]/ClientShell.tsx

@@ -0,0 +1,13 @@
+"use client";
+
+import dynamic from "next/dynamic";
+
+// The whole app is a client-side React Router SPA whose providers read window/localStorage during
+// their initial render -- ssr:false keeps Next's static prerender from ever executing any of it on
+// the server. Kept in its own client module so the route's page.tsx can stay a server component
+// (generateStaticParams is a server-only export and cannot live in a "use client" file).
+const ClientApp = dynamic(() => import("../../src/ClientApp"), { ssr: false });
+
+export default function ClientShell() {
+  return <ClientApp />;
+}

job-tracker-ui/app/[[...slug]]/page.tsx

@@ -0,0 +1,15 @@
+import ClientShell from "./ClientShell";
+
+// Optional catch-all so EVERY path (/, /cv/{slug}, /career/builder/…) resolves to this same shell on
+// a hard load. Without it, `output: export` only generates `/`, and Next's client renders its
+// not-found for any deep URL before React Router can route it — breaking refresh and shared links.
+// generateStaticParams emits just index.html (the empty slug); nginx (try_files $uri /index.html)
+// serves that shell for every unknown path, and this catch-all matches it client-side so React
+// Router takes over. See docs/architecture/frontend.md (SPA routing).
+export function generateStaticParams() {
+  return [{ slug: [] }];
+}
+
+export default function Page() {
+  return <ClientShell />;
+}

job-tracker-ui/app/page.tsx

@@ -1,12 +0,0 @@
-"use client";
-
-import dynamic from "next/dynamic";
-
-// The whole app is a client-side React Router SPA whose providers read window/localStorage
-// during their initial render -- ssr:false keeps Next's static prerender from ever executing
-// any of it on the server.
-const ClientApp = dynamic(() => import("../src/ClientApp"), { ssr: false });
-
-export default function Page() {
-  return <ClientApp />;
-}