fix(routing): give every lazy page its own ErrorBoundary

A render error in any route used to bubble all the way up to the single
page-level boundary at AppWithNavigator, replacing the entire shell
(sidebar, header, blocking overlays) with the contained error UI — even
if only one sub-page was broken.

Embed an ErrorBoundary inside LazyPage so the smallest meaningful unit
(a route's lazy chunk + its rendered tree) is the boundary scope. Shell
chrome stays alive, the user can navigate elsewhere, and chunk-load
failures still get the lazyWithRetry reload path because the boundary
sits outside Suspense.

src/App.tsx

@@ -200,9 +200,16 @@ function AdminRoute({ children }: { children: React.ReactNode }) {
   return <Layout>{children}</Layout>;
 }
 
-// Suspense wrapper for lazy components
+// Suspense + error boundary wrapper for lazy routes. The boundary lives
+// OUTSIDE Suspense so chunk-load failures (caught by lazyWithRetry's reload
+// path) and render-time exceptions both surface in the page-level fallback
+// instead of crashing the entire shell via the top-level boundary.
 function LazyPage({ children }: { children: React.ReactNode }) {
-  return <Suspense fallback={<PageLoader variant="dark" />}>{children}</Suspense>;
+  return (
+    <ErrorBoundary level="page">
+      <Suspense fallback={<PageLoader variant="dark" />}>{children}</Suspense>
+    </ErrorBoundary>
+  );
 }
 
 function BlockingOverlay() {