feat(App): implement code-splitting for improved performance and user experience

- Refactored the App component to utilize React's lazy loading for page components, enhancing load times and performance.
- Introduced a fallback UI with a spinner during component loading, improving user feedback during navigation.
- Updated the AuthContext to use useCallback and useMemo for optimized performance in login and logout functions, reducing unnecessary re-renders.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.jsx

@@ -1,4 +1,4 @@
-import React from 'react'
+import React, { Suspense, lazy } from 'react'
 import {
   RouterProvider,
   createBrowserRouter,
@@ -12,45 +12,66 @@ import { ToastProvider } from './context/ToastContext'
 import { OrgInboxProvider, useOrgInbox } from './context/OrgInboxContext'
 import DesktopSidebar from './components/DesktopSidebar'
 import { getMainNavItems } from './config/appNav'
-import LoginPage from './pages/LoginPage'
-import VerifyPage from './pages/VerifyPage'
-import Dashboard from './pages/Dashboard'
-import AccountSettingsPage from './pages/AccountSettingsPage'
-import SettingsSystemInfoPage from './pages/SettingsSystemInfoPage'
-import ExercisesListPage from './pages/ExercisesListPage'
-import ExerciseDetailPage from './pages/ExerciseDetailPage'
-import ExerciseFormPage from './pages/ExerciseFormPage'
-import ClubsPage from './pages/ClubsPage'
-import InboxPage from './pages/InboxPage'
-import SkillsPage from './pages/SkillsPage'
-import TrainingPlanningPage from './pages/TrainingPlanningPage'
-import TrainingFrameworkProgramsListPage from './pages/TrainingFrameworkProgramsListPage'
-import TrainingFrameworkProgramEditPage from './pages/TrainingFrameworkProgramEditPage'
-import TrainingModulesListPage from './pages/TrainingModulesListPage'
-import TrainingModuleEditPage from './pages/TrainingModuleEditPage'
-import TrainingUnitRunPage from './pages/TrainingUnitRunPage'
-import TrainingCoachPage from './pages/TrainingCoachPage'
-import AdminCatalogsPage from './pages/AdminCatalogsPage'
-import AdminHierarchyPage from './pages/AdminHierarchyPage'
-import AdminMaturityModelsPage from './pages/AdminMaturityModelsPage'
-import TrainerContextsPage from './pages/TrainerContextsPage'
-import MediaWikiImportPage from './pages/MediaWikiImportPage'
-import AdminUsersPage from './pages/AdminUsersPage'
 import AdminHomeRedirect from './components/AdminHomeRedirect'
 import PlatformAdminRoute from './components/PlatformAdminRoute'
-import MediaLibraryPage from './pages/MediaLibraryPage'
-import LegalPage from './pages/LegalPage'
-import AdminLegalDocumentsPage from './pages/AdminLegalDocumentsPage'
-import SettingsLegalPage from './pages/SettingsLegalPage'
 import ActiveClubSwitcher from './components/ActiveClubSwitcher'
 import InactiveMembershipBanner from './components/InactiveMembershipBanner'
 import './app.css'
 
+const LoginPage = lazy(() => import('./pages/LoginPage'))
+const VerifyPage = lazy(() => import('./pages/VerifyPage'))
+const Dashboard = lazy(() => import('./pages/Dashboard'))
+const AccountSettingsPage = lazy(() => import('./pages/AccountSettingsPage'))
+const SettingsSystemInfoPage = lazy(() => import('./pages/SettingsSystemInfoPage'))
+const ExercisesListPage = lazy(() => import('./pages/ExercisesListPage'))
+const ExerciseDetailPage = lazy(() => import('./pages/ExerciseDetailPage'))
+const ExerciseFormPage = lazy(() => import('./pages/ExerciseFormPage'))
+const ClubsPage = lazy(() => import('./pages/ClubsPage'))
+const InboxPage = lazy(() => import('./pages/InboxPage'))
+const SkillsPage = lazy(() => import('./pages/SkillsPage'))
+const TrainingPlanningPage = lazy(() => import('./pages/TrainingPlanningPage'))
+const TrainingFrameworkProgramsListPage = lazy(() =>
+  import('./pages/TrainingFrameworkProgramsListPage'),
+)
+const TrainingFrameworkProgramEditPage = lazy(() =>
+  import('./pages/TrainingFrameworkProgramEditPage'),
+)
+const TrainingModulesListPage = lazy(() => import('./pages/TrainingModulesListPage'))
+const TrainingModuleEditPage = lazy(() => import('./pages/TrainingModuleEditPage'))
+const TrainingUnitRunPage = lazy(() => import('./pages/TrainingUnitRunPage'))
+const TrainingCoachPage = lazy(() => import('./pages/TrainingCoachPage'))
+const AdminCatalogsPage = lazy(() => import('./pages/AdminCatalogsPage'))
+const AdminHierarchyPage = lazy(() => import('./pages/AdminHierarchyPage'))
+const AdminMaturityModelsPage = lazy(() => import('./pages/AdminMaturityModelsPage'))
+const TrainerContextsPage = lazy(() => import('./pages/TrainerContextsPage'))
+const MediaWikiImportPage = lazy(() => import('./pages/MediaWikiImportPage'))
+const AdminUsersPage = lazy(() => import('./pages/AdminUsersPage'))
+const MediaLibraryPage = lazy(() => import('./pages/MediaLibraryPage'))
+const LegalPage = lazy(() => import('./pages/LegalPage'))
+const AdminLegalDocumentsPage = lazy(() => import('./pages/AdminLegalDocumentsPage'))
+const SettingsLegalPage = lazy(() => import('./pages/SettingsLegalPage'))
+
 /** Shield „Admin“: nur Super-Admin (global). Vereinsorga: Vereine → Mitglieder. */
 function computeShowAdminNav(currentUser) {
   return currentUser?.role === 'superadmin'
 }
 
+function AppRouteFallback() {
+  return (
+    <div
+      style={{
+        minHeight: '100vh',
+        display: 'flex',
+        alignItems: 'center',
+        justifyContent: 'center',
+        background: 'var(--bg)',
+      }}
+    >
+      <div className="spinner"></div>
+    </div>
+  )
+}
+
 // Bottom Navigation (Mobile)
 function Nav({ showAdminNav }) {
   const { canAccessOrgInbox, inboxCount } = useOrgInbox()
@@ -270,7 +291,9 @@ function App() {
   return (
     <AuthProvider>
       <ToastProvider>
-        <RouterProvider router={appRouter} />
+        <Suspense fallback={<AppRouteFallback />}>
+          <RouterProvider router={appRouter} />
+        </Suspense>
       </ToastProvider>
     </AuthProvider>
   )

frontend/src/context/AuthContext.jsx

@@ -1,4 +1,12 @@
-import { createContext, useContext, useState, useEffect, useCallback, useRef } from 'react'
+import {
+  createContext,
+  useContext,
+  useState,
+  useEffect,
+  useCallback,
+  useMemo,
+  useRef,
+} from 'react'
 import api, { ACTIVE_CLUB_STORAGE_KEY } from '../utils/api'
 import { activeClubMemberships } from '../utils/activeClub'
 
@@ -94,7 +102,7 @@ export function AuthProvider({ children }) {
   }, [])
 
   /** Fallback, falls ohne checkAuth gesetzt wird (Legacy / Token-Injektion) */
-  const login = (payload) => {
+  const login = useCallback((payload) => {
     if (payload?.profile != null) {
       syncStoredActiveClub(payload.profile)
       setUser(payload.profile)
@@ -112,9 +120,9 @@ export function AuthProvider({ children }) {
       return
     }
     setUser(payload)
-  }
+  }, [])
 
-  const logout = () => {
+  const logout = useCallback(() => {
     setUser(null)
     localStorage.removeItem('authToken')
     localStorage.removeItem(ACTIVE_CLUB_STORAGE_KEY)
@@ -123,17 +131,20 @@ export function AuthProvider({ children }) {
         sessionStorage.removeItem(key)
       }
     }
-  }
+  }, [])
 
-  const value = {
-    user,
-    isAuthenticated: !!user,
-    loading,
-    login,
-    logout,
-    checkAuth,
-    setActiveClub,
-  }
+  const value = useMemo(
+    () => ({
+      user,
+      isAuthenticated: !!user,
+      loading,
+      login,
+      logout,
+      checkAuth,
+      setActiveClub,
+    }),
+    [user, loading, login, logout, checkAuth, setActiveClub],
+  )
 
   return (
     <AuthContext.Provider value={value}>

frontend/vite.config.js

@@ -9,6 +9,33 @@ export default defineConfig({
   },
   build: {
     outDir: 'dist',
-    sourcemap: false
-  }
+    sourcemap: false,
+    rollupOptions: {
+      output: {
+        manualChunks(id) {
+          if (!id.includes('node_modules')) return
+          if (id.includes('jspdf')) return 'vendor-pdf'
+          if (id.includes('lucide-react')) return 'vendor-icons'
+          if (
+            id.includes('react-markdown') ||
+            id.includes('/marked/') ||
+            id.includes('remark-') ||
+            id.includes('mdast') ||
+            id.includes('micromark') ||
+            id.includes('unist')
+          ) {
+            return 'vendor-markdown'
+          }
+          if (id.includes('react-router')) return 'vendor-router'
+          if (
+            /[/\\]node_modules[/\\]react-dom[/\\]/.test(id) ||
+            /[/\\]node_modules[/\\]react[/\\]/.test(id) ||
+            /[/\\]node_modules[/\\]scheduler[/\\]/.test(id)
+          ) {
+            return 'vendor-react'
+          }
+        },
+      },
+    },
+  },
 })