test(journey): fix FE-PAGE-JOURNEYDETAIL-027 flaky spinner assertion

Pre-seed the store into loading state before render instead of relying on
timing. RTL's render() flushes all microtasks via act(), so the MSW response
lands before render() returns, leaving no observable loading window.

client/src/pages/JourneyDetailPage.test.tsx

@@ -674,7 +674,10 @@ describe('JourneyDetailPage', () => {
   // ── FE-PAGE-JOURNEYDETAIL-027 ──────────────────────────────────────────
   describe('FE-PAGE-JOURNEYDETAIL-027: Shows loading spinner before data loads', () => {
     it('renders a spinner while journey data is loading', () => {
-      // Do NOT await the waitFor -- we check the loading state before data arrives
+      // Pre-seed the store into a loading state (current: null, loading: true).
+      // We can't rely on render() timing because RTL wraps in act(), which flushes
+      // all microtasks including the MSW response before render() returns.
+      useJourneyStore.setState({ loading: true, current: null });
       render(<JourneyDetailPage />);
       // The spinner has animate-spin class on a div
       const spinner = document.querySelector('.animate-spin');