feat: add /litters/:id route for LitterDetail page

client/src/App.jsx

@@ -5,6 +5,7 @@ import DogList from './pages/DogList'
 import DogDetail from './pages/DogDetail'
 import PedigreeView from './pages/PedigreeView'
 import LitterList from './pages/LitterList'
+import LitterDetail from './pages/LitterDetail'
 import BreedingCalendar from './pages/BreedingCalendar'
 import PairingSimulator from './pages/PairingSimulator'
 import './App.css'
@@ -55,6 +56,7 @@ function App() {
             <Route path="/dogs/:id" element={<DogDetail />} />
             <Route path="/pedigree/:id" element={<PedigreeView />} />
             <Route path="/litters" element={<LitterList />} />
+            <Route path="/litters/:id" element={<LitterDetail />} />
             <Route path="/breeding" element={<BreedingCalendar />} />
             <Route path="/pairing" element={<PairingSimulator />} />
           </Routes>