refactor(client): split feature chunks and polish environment ui

- lazy-load route pages and add entity-based manual chunking in Vite

- prevent environment pages from crashing when legacy records miss data

- fix sidebar toggle chevron direction and make env forms full width

client/src/pages/environment/EnvironmentsPage.tsx

@@ -20,7 +20,7 @@ import styles from '../Page.module.css';
 function EnvironmentCard({ env, onDelete }: { env: Environment; onDelete: (id: string) => void }) {
   const { t } = useTranslation();
   const navigate = useNavigate();
-  const dataEntries = Object.entries(env.data).filter(([, v]) => v);
+  const dataEntries = Object.entries(env.data ?? {}).filter(([, v]) => v);
 
   const handleExport = async () => {
     const data = await environments.exportEnvironment(env.id);