fix(router): replace legacy redirects with NotFoundPage to prevent redirect loop

The `:specId/:library` catch-all route was matching `/python/scatter-basic`
(specId=python, library=scatter-basic) instead of the `python` route group,
causing an infinite `/python/python/python/...` redirect loop.

Replace all legacy redirect routes with a simple `*` catch-all that renders
NotFoundPage. The site is young enough that old URLs don't need preservation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: MarkusNeusinger

app/src/router.tsx

@@ -1,40 +1,18 @@
-import { createBrowserRouter, RouterProvider, Navigate, useParams } from 'react-router-dom';
+import { createBrowserRouter, RouterProvider } from 'react-router-dom';
 import { HelmetProvider } from 'react-helmet-async';
 import Box from '@mui/material/Box';
 import CircularProgress from '@mui/material/CircularProgress';
 import { Layout, AppDataProvider } from './components/Layout';
 import { ErrorBoundary } from './components/ErrorBoundary';
 import { HomePage } from './pages/HomePage';
 import { NotFoundPage } from './pages/NotFoundPage';
-import { specPath, interactivePath } from './utils/paths';
 
 const LazyFallback = () => (
   <Box sx={{ display: 'flex', justifyContent: 'center', alignItems: 'center', minHeight: '50vh' }}>
     <CircularProgress size={32} />
   </Box>
 );
 
-// Catches old URLs without /python/ prefix and redirects to /python/ equivalents.
-// Uses splat (*) to avoid route ranking conflicts with the python route group.
-function LegacyCatchAll() {
-  const params = useParams();
-  const splatPath = params['*'] || '';
-  const parts = splatPath.split('/').filter(Boolean);
-
-  if (parts.length === 1) {
-    return <Navigate to={specPath(parts[0])} replace />;
-  }
-  if (parts.length === 2) {
-    return <Navigate to={specPath(parts[0], parts[1])} replace />;
-  }
-  return <NotFoundPage />;
-}
-
-function LegacyInteractiveRedirect() {
-  const { specId, library } = useParams();
-  return <Navigate to={interactivePath(specId!, library!)} replace />;
-}
-
 const lazySpec = () => import('./pages/SpecPage').then(m => ({ Component: m.SpecPage, HydrateFallback: LazyFallback }));
 
 const router = createBrowserRouter([
@@ -54,15 +32,12 @@ const router = createBrowserRouter([
         { path: ':specId', lazy: lazySpec },
         { path: ':specId/:library', lazy: lazySpec },
       ]},
-      // Legacy catch-all: redirects old /:specId and /:specId/:library to /python/ equivalents.
-      // Uses * (lowest priority) so the python route group always wins.
-      { path: '*', element: <LegacyCatchAll /> },
+      // Old URLs without /python/ prefix → redirect to homepage
+      { path: '*', element: <NotFoundPage /> },
     ],
   },
   // Fullscreen interactive view (outside Layout)
   { path: 'python/interactive/:specId/:library', lazy: () => import('./pages/InteractivePage').then(m => ({ Component: m.InteractivePage, HydrateFallback: LazyFallback })) },
-  // Legacy interactive redirect
-  { path: 'interactive/:specId/:library', element: <LegacyInteractiveRedirect /> },
   // Hidden debug dashboard (outside Layout - no header/footer)
   { path: 'debug', lazy: () => import('./pages/DebugPage').then(m => ({ Component: m.DebugPage, HydrateFallback: LazyFallback })) },
   { path: '*', element: <NotFoundPage /> },