feat: add public user profiles

- Add GET /api/users/:username endpoint for public profiles
- Create PublicProfilePage component with user stats and info
- Add getUserByUsername function to API service
- Add /:username route to App.jsx
- Display user info: name, location, stats, WSDC ID, social links
- Only show public data (no email or sensitive information)
- Accessible only to authenticated users

Users can now view public profiles of other users by visiting
/<username>. The profile displays stats, location, WSDC ID, and
social media links.

frontend/src/App.jsx

@@ -11,6 +11,7 @@ import MatchChatPage from './pages/MatchChatPage';
 import RatePartnerPage from './pages/RatePartnerPage';
 import HistoryPage from './pages/HistoryPage';
 import ProfilePage from './pages/ProfilePage';
+import PublicProfilePage from './pages/PublicProfilePage';
 import VerificationBanner from './components/common/VerificationBanner';
 
 // Protected Route Component with Verification Banner
@@ -132,9 +133,18 @@ function App() {
             }
           />
 
+          {/* Public Profile - must be before default redirect */}
+          <Route
+            path="/:username"
+            element={
+              <ProtectedRoute>
+                <PublicProfilePage />
+              </ProtectedRoute>
+            }
+          />
+
           {/* Default redirect */}
           <Route path="/" element={<Navigate to="/events" replace />} />
-          <Route path="*" element={<Navigate to="/events" replace />} />
         </Routes>
       </AuthProvider>
     </BrowserRouter>