feat(nav): add External Dogs nav link and route

client/src/App.jsx

@@ -1,5 +1,5 @@
 import { BrowserRouter as Router, Routes, Route, Link, useLocation } from 'react-router-dom'
-import { Home, PawPrint, Activity, Heart, FlaskConical, Settings } from 'lucide-react'
+import { Home, PawPrint, Activity, Heart, FlaskConical, Settings, ExternalLink } from 'lucide-react'
 import Dashboard from './pages/Dashboard'
 import DogList from './pages/DogList'
 import DogDetail from './pages/DogDetail'
@@ -9,6 +9,7 @@ import LitterDetail from './pages/LitterDetail'
 import BreedingCalendar from './pages/BreedingCalendar'
 import PairingSimulator from './pages/PairingSimulator'
 import SettingsPage from './pages/SettingsPage'
+import ExternalDogs from './pages/ExternalDogs'
 import { useSettings } from './hooks/useSettings'
 import './App.css'
 
@@ -42,6 +43,7 @@ function AppInner() {
           <div className="nav-links">
             <NavLink to="/" icon={Home} label="Dashboard" />
             <NavLink to="/dogs" icon={PawPrint} label="Dogs" />
+            <NavLink to="/external" icon={ExternalLink} label="External" />
             <NavLink to="/litters" icon={Activity} label="Litters" />
             <NavLink to="/breeding" icon={Heart} label="Breeding" />
             <NavLink to="/pairing" icon={FlaskConical} label="Pairing" />
@@ -55,6 +57,7 @@ function AppInner() {
           <Route path="/" element={<Dashboard />} />
           <Route path="/dogs" element={<DogList />} />
           <Route path="/dogs/:id" element={<DogDetail />} />
+          <Route path="/external" element={<ExternalDogs />} />
           <Route path="/pedigree/:id" element={<PedigreeView />} />
           <Route path="/litters" element={<LitterList />} />
           <Route path="/litters/:id" element={<LitterDetail />} />