feat: 登录持久化修复 + 左下角账号区 + 管理页面（管理员/邀请码）

app/src/App.tsx

@@ -9,6 +9,7 @@ const DashboardPage = lazy(() => import('@/pages/dashboard/DashboardPage').then(
 const GradesPage = lazy(() => import('@/pages/grades/GradesPage').then(m => ({ default: m.GradesPage })));
 const TypesPage = lazy(() => import('@/pages/types/TypesPage').then(m => ({ default: m.TypesPage })));
 const TaxonomyPage = lazy(() => import('@/pages/taxonomy/TaxonomyPage').then(m => ({ default: m.TaxonomyPage })));
+const AdminPage = lazy(() => import('@/pages/admin/AdminPage').then(m => ({ default: m.AdminPage })));
 
 function PageLoading() {
   return <div className="py-16 text-center text-[13px] text-ink-3">加载中…</div>;
@@ -25,6 +26,7 @@ export default function App() {
         <Route path="/dashboard" element={<Suspense fallback={<PageLoading />}><DashboardPage /></Suspense>} />
         <Route path="/types" element={<Suspense fallback={<PageLoading />}><TypesPage /></Suspense>} />
         <Route path="/taxonomy" element={<Suspense fallback={<PageLoading />}><TaxonomyPage /></Suspense>} />
+        <Route path="/admin" element={<Suspense fallback={<PageLoading />}><AdminPage /></Suspense>} />
         <Route path="*" element={<Navigate to="/timeline" replace />} />
       </Route>
     </Routes>