Show a recovery screen for app render errors (#1924)

* fix(app): show recovery screen for render failures

Render a retryable fallback with useful error details when the routed app tree throws during render instead of leaving the app blank.

* test(app): cover root error details without mounting

Move caught-value formatting into a pure module, cover AggregateError fields without duplicate output, and remove the component-mounted test.

* fix(app): keep empty error details caught

* fix(app): preserve nullable aggregate errors

* fix(app): guard malformed error details

* fix(app): handle recursive error causes

* fix(app): guard error detail formatting failures

* fix(app): localize root error fallback

* fix(app): keep root error fallback on existing i18n

packages/app/src/i18n/resources/fr.ts

@@ -1086,6 +1086,12 @@ export const fr: TranslationResources = {
       },
     },
   },
+  rootError: {
+    kicker: "Une erreur s'est produite",
+    title: "Paseo a rencontré un problème.",
+    body: "Réessayez pour recharger l'application. Si cela continue, joignez les détails ci-dessous au signalement.",
+    details: "Détails",
+  },
   startup: {
     errorTitle: "Quelque chose s'est mal passé",
     errorDescription: