feat(frontend): router restructure /admin → /lessons with redirects

packages/frontend/src/components/LessonTree.tsx

@@ -114,7 +114,7 @@ function TreeRow({ n, depth }: { n: LessonTreeNode; depth: number }) {
           >⋮⋮</span>
         )}
         <span className={`h-2 w-2 rounded-full ${depth === 0 ? 'bg-brand-500' : 'bg-brand-300'}`} />
-        <Link to={`/admin/lessons/${n.id}`} className="flex-1 truncate font-medium text-slate-800 dark:text-slate-100">
+        <Link to={`/lessons/${n.id}`} className="flex-1 truncate font-medium text-slate-800 dark:text-slate-100">
           {n.name}
           <span className="ml-2 rounded-full bg-brand-100 px-2 py-0.5 text-xs font-semibold text-brand-700 dark:bg-brand-900/30 dark:text-brand-200">
             {n.cardCount}

packages/frontend/src/pages/Marketplace.tsx

@@ -33,7 +33,7 @@ export function MarketplacePage() {
   async function fork(id: number) {
     try {
       const f = await lessonsApi.fork(id);
-      navigate(`/admin/lessons/${f.id}`);
+      navigate(`/lessons/${f.id}`);
     }
     catch (e) { alert(e instanceof ApiClientError ? e.message : 'Forken mislukt'); }
   }

packages/frontend/src/router.tsx

@@ -1,10 +1,9 @@
 import { lazy, Suspense, type ComponentType } from 'react';
-import { createBrowserRouter, Navigate } from 'react-router-dom';
+import { createBrowserRouter, Navigate, useParams } from 'react-router-dom';
 import { Layout } from './components/Layout.js';
 import { AuthBoundary } from './components/AuthBoundary.js';
 import { RoleGuard } from './components/RoleGuard.js';
 
-// Tiny loading placeholder reused for every lazy route boundary.
 function PageFallback() {
   return (
     <div className="flex h-full items-center justify-center p-12">
@@ -13,8 +12,6 @@ function PageFallback() {
   );
 }
 
-// `React.lazy` requires a default export; our pages use named exports, so we
-// adapt with a small helper that picks the named export from the module.
 function lazyPage<K extends string>(
   loader: () => Promise<Record<K, ComponentType>>,
   name: K,
@@ -33,8 +30,8 @@ function lazyPage<K extends string>(
 }
 
 const Dashboard = lazyPage(() => import('./pages/Dashboard.js'), 'DashboardPage');
-const Admin = lazyPage(() => import('./pages/Admin.js'), 'AdminPage');
-const AdminLesson = lazyPage(() => import('./pages/AdminLesson.js'), 'AdminLessonPage');
+const Lessons = lazyPage(() => import('./pages/Lessons.js'), 'LessonsPage');
+const LessonDetail = lazyPage(() => import('./pages/LessonDetail.js'), 'LessonDetailPage');
 const PracticeSetup = lazyPage(() => import('./pages/PracticeSetup.js'), 'PracticeSetupPage');
 const Practice = lazyPage(() => import('./pages/Practice.js'), 'PracticePage');
 const PracticeDone = lazyPage(() => import('./pages/PracticeDone.js'), 'PracticeDonePage');
@@ -53,12 +50,17 @@ const ForgotPassword = lazyPage(() => import('./pages/auth/ForgotPassword.js'),
 const ResetPassword = lazyPage(() => import('./pages/auth/ResetPassword.js'), 'ResetPasswordPage');
 const AcceptInvite = lazyPage(() => import('./pages/auth/AcceptInvite.js'), 'AcceptInvitePage');
 
+function AdminToLessons() { return <Navigate to="/lessons" replace />; }
+function AdminLessonRedirect() {
+  const { id } = useParams();
+  return <Navigate to={`/lessons/${id ?? ''}`} replace />;
+}
+
 export const router = createBrowserRouter([
   {
     path: '/',
     element: <Layout />,
     children: [
-      // Public auth routes
       { path: 'login', element: <Login /> },
       { path: 'register', element: <Register /> },
       { path: 'verify-email', element: <VerifyEmail /> },
@@ -66,13 +68,16 @@ export const router = createBrowserRouter([
       { path: 'reset-password', element: <ResetPassword /> },
       { path: 'accept-invite', element: <AcceptInvite /> },
 
-      // Authenticated routes
       {
         element: <AuthBoundary />,
         children: [
           { index: true, element: <Dashboard /> },
-          { path: 'admin', element: <Admin /> },
-          { path: 'admin/lessons/:id', element: <AdminLesson /> },
+          { path: 'lessons', element: <Lessons /> },
+          { path: 'lessons/:id', element: <LessonDetail /> },
+
+          { path: 'admin', element: <AdminToLessons /> },
+          { path: 'admin/lessons/:id', element: <AdminLessonRedirect /> },
+
           { path: 'practice/:lessonId/setup', element: <PracticeSetup /> },
           { path: 'practice/:lessonId', element: <Practice /> },
           { path: 'practice/:lessonId/done', element: <PracticeDone /> },