test(welcome): align Router/Step1/Step2 stub routes with /home destination

Post-refactor, WelcomeRouter and the Step1/Step2 "Skip-the-rest" handlers
navigate to /home, but the MemoryRouter test stubs still mounted the
"dashboard" marker at /. Update the stub routes (and matching it() titles)
so the assertions resolve.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/pages/welcome/__tests__/WelcomeStep1.test.tsx

@@ -65,7 +65,7 @@ function renderPage() {
       <Routes>
         <Route path="/welcome/step-1" element={<WelcomeStep1 />} />
         <Route path="/welcome/step-2" element={<div>step-2</div>} />
-        <Route path="/" element={<div>dashboard</div>} />
+        <Route path="/home" element={<div>dashboard</div>} />
       </Routes>
     </MemoryRouter>,
   )
@@ -148,7 +148,7 @@ describe('WelcomeStep1', () => {
     })
   })
 
-  it('Skip-the-rest dismisses and navigates to /', async () => {
+  it('Skip-the-rest dismisses and navigates to /home', async () => {
     const user = userEvent.setup()
     renderPage()