fix(routing): finish /home migration in WelcomeStep3 + VerifyEmailPage

The original public-landing routing refactor migrated WelcomeRouter,
WelcomeStep1, and WelcomeStep2 post-onboarding redirects to /home, but
left four sites still pointing at the old / + query-string destinations:

  - WelcomeStep3 `completeWizardAndExit` (Send invites)
  - WelcomeStep3 `handleSkipStep` (Skip)
  - VerifyEmailPage post-verify auto-redirect (`setTimeout`)
  - VerifyEmailPage success-state "Go to dashboard" Link

These all worked by accident because PublicLanding redirects authed
users from / to /home — so users still landed on the dashboard, but
through an unnecessary mount-and-redirect flicker, and the
`?welcome=true` / `?verified=1` query markers got dropped on the way.

Drop both query markers — neither is read anywhere in the codebase
(grepped frontend/src; the dashboard's onboarding UX is driven by
`getOnboardingStatus`, not URL state). Carrying dead URL params
just invites future "is this load-bearing?" investigations.

Test stubs in WelcomeStep3.test.tsx and VerifyEmailPage.test.tsx
moved from `<Route path="/">` to `<Route path="/home">` so the
assertions verify the new destination instead of accidentally matching
the old one (the previous stubs masked the partial migration).

Out of scope: AcceptInvitePage and OAuthCallbackPage still use
`?welcome=teammate`, but that one carries an explicit "decoded by the
dashboard in Task 41" annotation and may be wired up later, so left
untouched.

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

frontend/src/pages/VerifyEmailPage.tsx

@@ -20,8 +20,7 @@ const SUCCESS_REDIRECT_MS = 1200
  *   "Already verified" state. No API call.
  * - Else fire `POST /auth/email/verify` exactly once (a `useRef` guard keeps
  *   React 19 strict-mode double-invoke from double-firing the call). On
- *   success, refresh the auth store and bounce to `/?verified=1` so the
- *   dashboard surfaces a toast.
+ *   success, refresh the auth store and bounce to `/home`.
  * - On error, show "Invalid or expired token" + a "Resend" CTA that calls
  *   `POST /auth/email/send-verification`.
  */
@@ -70,10 +69,9 @@ export function VerifyEmailPage() {
         if (cancelled) return
         setStatus('success')
         toast.success('Email verified')
-        // Brief success state, then redirect with a query flag so the
-        // dashboard can re-surface confirmation if it wants to.
+        // Brief success state, then redirect to the dashboard.
         window.setTimeout(() => {
-          navigate('/?verified=1', { replace: true })
+          navigate('/home', { replace: true })
         }, SUCCESS_REDIRECT_MS)
       })
       .catch((err) => {
@@ -126,7 +124,7 @@ export function VerifyEmailPage() {
                 Redirecting you to the dashboard…
               </p>
               <Link
-                to="/?verified=1"
+                to="/home"
                 replace
                 className={cn(
                   'mt-6 inline-flex items-center rounded-lg bg-primary px-6 py-2 text-sm font-semibold text-primary-foreground',

frontend/src/pages/__tests__/VerifyEmailPage.test.tsx

@@ -52,7 +52,7 @@ function renderPage(initialPath: string) {
       <MemoryRouter initialEntries={[initialPath]}>
         <Routes>
           <Route path="/verify-email" element={<VerifyEmailPage />} />
-          <Route path="/" element={<div>dashboard</div>} />
+          <Route path="/home" element={<div>dashboard</div>} />
         </Routes>
       </MemoryRouter>
     </HelmetProvider>,
@@ -130,7 +130,7 @@ describe('VerifyEmailPage', () => {
         <MemoryRouter initialEntries={['/verify-email?token=valid-token']}>
           <Routes>
             <Route path="/verify-email" element={<VerifyEmailPage />} />
-            <Route path="/" element={<div>dashboard</div>} />
+            <Route path="/home" element={<div>dashboard</div>} />
           </Routes>
         </MemoryRouter>
       </HelmetProvider>,
@@ -142,7 +142,7 @@ describe('VerifyEmailPage', () => {
         <MemoryRouter initialEntries={['/verify-email?token=valid-token']}>
           <Routes>
             <Route path="/verify-email" element={<VerifyEmailPage />} />
-            <Route path="/" element={<div>dashboard</div>} />
+            <Route path="/home" element={<div>dashboard</div>} />
           </Routes>
         </MemoryRouter>
       </HelmetProvider>,

frontend/src/pages/welcome/WelcomeStep3.tsx

@@ -39,7 +39,7 @@ function makeEmptyRow(): InviteRow {
  *
  *   1. POST `/accounts/me/invites/bulk` with populated rows.
  *   2. PATCH `/users/me/onboarding-step` `{step: 3, action: "complete"}`.
- *   3. Navigate to `/?welcome=true` and fire a "You're all set" toast.
+ *   3. Navigate to `/home` and fire a "You're all set" toast.
  *
  * Partial-failure UX: rows in `failed[]` keep their input and show an
  * inline error. The wizard does NOT auto-advance when there are failures —
@@ -109,7 +109,7 @@ export function WelcomeStep3() {
     await onboardingApi.updateStep({ step: 3, action: 'complete' })
     await fetchUser()
     toast.success("You're all set!")
-    navigate('/?welcome=true')
+    navigate('/home')
   }
 
   const handleSendInvites = async () => {
@@ -177,7 +177,7 @@ export function WelcomeStep3() {
       await onboardingApi.updateStep({ step: 3, action: 'skip' })
       await fetchUser()
       toast.success("You're all set!")
-      navigate('/?welcome=true')
+      navigate('/home')
     } catch {
       setError('Could not save. Please try again.')
       setSubmitting(null)

frontend/src/pages/welcome/__tests__/WelcomeStep3.test.tsx

@@ -88,7 +88,7 @@ function renderPage() {
     <MemoryRouter initialEntries={['/welcome/step-3']}>
       <Routes>
         <Route path="/welcome/step-3" element={<WelcomeStep3 />} />
-        <Route path="/" element={<div>dashboard</div>} />
+        <Route path="/home" element={<div>dashboard</div>} />
       </Routes>
     </MemoryRouter>,
   )