webv2: localize queue runtime error messages and notification titles #9945

Follow-up from the review of #9858.

The webv2 queue runtime (invokeai/frontend/webv2/src/features/queue/runtime.ts) stores failure text as plain strings in the queue item's errorMessage via commands.setStatus({ error }). That text is then shown as-is:

• in QueueItemDetails.tsx (item.errorMessage)
• in the run-outcome notifications in workbenchState.ts, whose titles are also hard-coded English (e.g. 'Invocation failed')

The runtime has no i18n hook outside React, so none of these strings can be translated today. This covers the server-error (5xx) failure from #9858, but also the other runtime error strings.

Possible approach: store a stable error code alongside the raw server detail, e.g. { code: 'server_error', detail }, and have the React views render a localized string from public/locales/en.json, with the server text as secondary detail. The notification titles would move to translation keys the same way.