Add employee code assignment function

src/App.tsx

@@ -7,6 +7,7 @@ import DashboardPage from './pages/Dashboard';
 import GeneratePage from './pages/Generate';
 import ManagePage from './pages/Manage';
 import ProfilePage from './pages/Profile';
+import EmployeeSerialsPage from './pages/EmployeeSerials';
 
 const PrivateRoute = () => {
   const user = authApi.getCurrentUser();
@@ -50,6 +51,7 @@ function App() {
             <Route path="/admin/dashboard" element={<DashboardPage />} />
             <Route path="/admin/generate" element={<GeneratePage />} />
             <Route path="/admin/manage" element={<ManagePage />} />
+            <Route path="/admin/employee-serials" element={<EmployeeSerialsPage />} />
             <Route path="/admin/profile" element={<ProfilePage />} />
           </Route>
         </Route>