Add admin functionality and improve UI styling

frontend/src/App.tsx

@@ -6,6 +6,7 @@ import { Container } from '@mui/material';
 import EventList from './components/EventList';
 import EventForm from './components/EventForm';
 import RSVPForm from './components/RSVPForm';
+import EventAdmin from './components/EventAdmin';
 import './App.css';
 
 const darkTheme = createTheme({
@@ -41,6 +42,7 @@ const App: React.FC = () => {
                 <Route path="/" element={<EventList />} />
                 <Route path="/create" element={<EventForm />} />
                 <Route path="/events/:slug/rsvp" element={<RSVPForm />} />
+                <Route path="/events/:slug/admin" element={<EventAdmin />} />
               </Routes>
             </div>
           </main>