feat(web): UDT-003 formulario de alta de usuarios (admin)

Agrega CreateUserPage con UserForm (react-hook-form + Zod), hook useCreateUser
(TanStack Query mutation), ruta /users/new protegida y entrada en AppSidebar.
Incluye tests Vitest: UserForm (9 casos) y useCreateUser (3 casos).

src/web/src/router.tsx

@@ -1,6 +1,7 @@
 import { Navigate, Route, Routes } from 'react-router-dom'
 import { useAuthStore } from './stores/authStore'
 import { LoginPage } from './features/auth/pages/LoginPage'
+import { CreateUserPage } from './features/users/pages/CreateUserPage'
 import { HomePage } from './pages/HomePage'
 import { PublicLayout } from './layouts/PublicLayout'
 import { ProtectedLayout } from './layouts/ProtectedLayout'
@@ -44,6 +45,16 @@ export function AppRoutes() {
           </ProtectedRoute>
         }
       />
+      <Route
+        path="/usuarios/nuevo"
+        element={
+          <ProtectedRoute>
+            <ProtectedLayout>
+              <CreateUserPage />
+            </ProtectedLayout>
+          </ProtectedRoute>
+        }
+      />
       <Route path="*" element={<Navigate to="/" replace />} />
     </Routes>
   )