[upstream #16998] #16998: Report a failed TTS cache delete in Settings #324

Codex finding on LibreChat-AI#16998: LibreChat-AI#16998 (comment)

Settings > Data > "Delete TTS cache" (client/src/components/Nav/SettingsTabs/Data/DeleteCache.tsx) has no failure state. When Cache Storage rejects the delete, the confirmation closes as if the cached audio were gone. Before LibreChat-AI#16998 the rejection escaped revokeAllUserKeys unhandled and left the spinner on; after it, clearTTSCache swallows the error so session teardown stays best effort.

Proposed fix: give the manual action a strict path (for example clearTTSCache returning whether the delete succeeded, or a separate strict variant), re-run checkCache after the action so the control reflects what is actually stored, and show a localized error toast with a retry when the delete fails. Needs one new English key in client/src/locales/en/translation.json.

Pre-existing on the base: the Settings action never reported a failed delete.