feat(stats): add stats page and pile trend

Show the stat groups on /stats, the pile trend on the dashboard card,
one switch per group in the settings, and the shared groups on the
public profile.

src/App.jsx

@@ -12,6 +12,7 @@ import GameLibrary from './pages/GameLibrary.jsx';
 import GameDetail from './pages/GameDetail.jsx';
 import WishlistPage from './pages/WishlistPage.jsx';
 import PlayNextPage from './pages/PlayNextPage.jsx';
+import StatsPage from './pages/StatsPage.jsx';
 import PublicProfilePage from './pages/PublicProfilePage.jsx';
 import AppHeader from './components/AppHeader.jsx';
 import {Toaster} from '@/components/ui/sonner';
@@ -67,6 +68,7 @@ function App() {
                         <Route path="/library/:appid" element={<GameDetail/>}/>
                         <Route path="/wishlist" element={<WishlistPage/>}/>
                         <Route path="/play-next" element={<PlayNextPage/>}/>
+                        <Route path="/stats" element={<StatsPage/>}/>
                         <Route path="/u/:name" element={<PublicProfilePage/>}/>
                         <Route path="/settings" element={<SettingsPage/>}/>
                         <Route path="/impressum" element={<ImprintPage/>}/>