feat(09-04): wire admin login redirect in LoginView.vue (D-08)

- After successful login, admin users redirect to /admin; regular users to /
- Honors ?redirect= query param for non-admin users as before
- authStore.user.role is synchronously populated before handleLoginResult fires

frontend/src/views/auth/LoginView.vue

@@ -216,8 +216,9 @@ function resetToPassword() {
 
 async function handleLoginResult(result) {
   if (!result) {
-    // Full success — tokens set in store
-    const redirect = route.query.redirect || '/'
+    // Full success — tokens set in store; admin users land at /admin (D-08)
+    const defaultRedirect = authStore.user?.role === 'admin' ? '/admin' : '/'
+    const redirect = route.query.redirect || defaultRedirect
     await router.push(redirect)
     return
   }