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/components/DashboardView.tsx

@@ -23,6 +23,7 @@ import AutoGraphIcon from "@mui/icons-material/AutoGraph";
 
 import { api } from "../api";
 import ViewStateNotice from "./ViewStateNotice";
+import OnboardingChecklist from "./OnboardingChecklist";
 import { getUserKeyFromToken } from "../themePrefs";
 import { useI18n } from "../i18n/I18nProvider";
 import { statusLabel } from "../pipeline";
@@ -287,6 +288,7 @@ export default function DashboardView() {
 
   return (
     <Box>
+      <OnboardingChecklist hasJobs={(stats?.total ?? 0) > 0} />
       <SectionCard
         sx={{
           backgroundColor: "background.paper",