fix: add missing route for feedback management page

- Added /admin/events/:id/feedback route to App.tsx
- This fixes the empty page issue when navigating to feedback management
- EventFeedbackPage component was already implemented but route was missing

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/App.tsx

@@ -16,6 +16,7 @@ import {
   EventsListPage,
   CreateEventPageEnhanced as CreateEventPage,
   EventDetailsPage,
+  EventFeedbackPage,
   EmailConfigPage,
   ArchivesPage,
   AnalyticsPage,
@@ -120,6 +121,7 @@ function App() {
                       <Route path="events" element={<EventsListPage />} />
                       <Route path="events/new" element={<CreateEventPage />} />
                       <Route path="events/:id" element={<EventDetailsPage />} />
+                      <Route path="events/:id/feedback" element={<EventFeedbackPage />} />
                       <Route path="archives" element={<ArchivesPage />} />
                       <Route path="email" element={<EmailConfigPage />} />
                       <Route path="analytics" element={<AnalyticsPage />} />