feat(ux): onboarding checklist, dashboard-first landing (fixed)

Dashboard onboarding checklist: a dismissible card with 3 steps (add
CV, import first job, check match score), each linking straight to
where you'd do it. Auto-hides once both CV and a job exist; otherwise
persists per-user via localStorage until dismissed.

Fixes the actual authenticated-landing redirect to /dashboard: my
earlier commit changed App.tsx's inner Shell route for "/", which
turned out to be dead code -- the outer router claims "/" for
LandingPage first, so Shell's own "/" route is never reached on a
direct hit. The real redirect lives in LandingPage.tsx's post-auth-check
navigate() and LoginPage.tsx's post-login nextPath default; both now
point at /dashboard. Verified live: an authenticated visitor hitting
"/" now lands on Dashboard with the onboarding checklist visible,
confirmed via rendered page text and screenshot.

job-tracker-ui/src/views/LandingPage.tsx

@@ -50,7 +50,7 @@ export default function LandingPage() {
     let active = true;
     api
       .get("/auth/me")
-      .then(() => { if (active) navigate("/jobs", { replace: true }); })
+      .then(() => { if (active) navigate("/dashboard", { replace: true }); })
       .catch(() => { if (active) setChecking(false); });
     return () => { active = false; };
   }, [navigate]);

job-tracker-ui/src/views/LoginPage.tsx

@@ -33,7 +33,7 @@ export default function LoginPage() {
   const [rememberMe, setRememberMe] = useState(() => getRememberMePref());
   const [loading, setLoading] = useState(false);
 
-  const nextPath = (location?.state?.from as string | undefined) ?? "/jobs";
+  const nextPath = (location?.state?.from as string | undefined) ?? "/dashboard";
 
   useEffect(() => {
     api