fix(frontend): remove unused variables causing tsc build failure

Remove unused `auth` prop from AdminPage (and its call site in App.tsx)
and unused `maxDate` variable in PlannerPage. Both triggered TS6133 under
noUnusedLocals, causing `npm run build` to exit with code 2 in Docker.

src/frontend/src/App.tsx

@@ -40,7 +40,7 @@ export default function App() {
       <Route path="/" element={<PlannerPage auth={auth} onLogout={handleLogout} />} />
       <Route
         path="/admin"
-        element={auth.isAdmin ? <AdminPage auth={auth} onLogout={handleLogout} /> : <Navigate to="/" replace />}
+        element={auth.isAdmin ? <AdminPage onLogout={handleLogout} /> : <Navigate to="/" replace />}
       />
       <Route path="*" element={<Navigate to="/" replace />} />
     </Routes>

src/frontend/src/pages/AdminPage.tsx

@@ -1,7 +1,7 @@
 import { useEffect, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { api } from '../api/client';
-import type { AdminUser, AuthResponse } from '../api/types';
+import type { AdminUser } from '../api/types';
 
 const PURPLE = '#5b4fc7';
 const PURPLE_DEEP = '#3f33a8';
@@ -10,7 +10,6 @@ const SAGE_DEEP = '#a9bb96';
 const PAPER = '#f4f3ee';
 
 interface AdminPageProps {
-  auth: AuthResponse;
   onLogout: () => void;
 }
 
@@ -18,7 +17,7 @@ function monogram(name: string): string {
   return name.split(' ').map((n) => n[0]).join('').slice(0, 2).toUpperCase();
 }
 
-export function AdminPage({ auth, onLogout }: AdminPageProps) {
+export function AdminPage({ onLogout }: AdminPageProps) {
   const navigate = useNavigate();
   const [users, setUsers] = useState<AdminUser[]>([]);
   const [loading, setLoading] = useState(true);

src/frontend/src/pages/PlannerPage.tsx

@@ -84,7 +84,6 @@ export function PlannerPage({ auth, onLogout }: PlannerPageProps) {
 
   const today = toIsoDate(new Date());
   const MAX_OFFSET = 13;
-  const maxDate = offsetDate(today, MAX_OFFSET);
 
   const [selectedDate, setSelectedDate] = useState(today);
   const [schedule, setSchedule] = useState<WorkplaceScheduleItem[]>([]);