🫧 refactor: Clear Drafts and Surface Error on Expired SSE Stream (#12309)

* refactor: error handling in useResumableSSE for 404 responses

- Added logic to clear drafts from localStorage when a 404 error occurs.
- Integrated errorHandler to notify users of the error condition.
- Introduced comprehensive tests to validate the new behavior, ensuring drafts are cleared and error handling is triggered correctly.C

* feat: add STREAM_EXPIRED error handling and message localization

- Introduced handling for STREAM_EXPIRED errors in useResumableSSE, updating errorHandler to provide relevant feedback.
- Added a new error message for STREAM_EXPIRED in translation files for user notifications.
- Updated tests to ensure proper error handling and message verification for STREAM_EXPIRED scenarios.

* refactor: replace clearDraft with clearAllDrafts utility

- Removed the clearDraft function from useResumableSSE and useSSE hooks, replacing it with the new clearAllDrafts utility for better draft management.
- Updated localStorage interactions to ensure both text and file drafts are cleared consistently for a conversation.
- Enhanced code readability and maintainability by centralizing draft clearing logic.

client/src/utils/drafts.ts

@@ -1,10 +1,17 @@
 import debounce from 'lodash/debounce';
-import { LocalStorageKeys } from 'librechat-data-provider';
+import { Constants, LocalStorageKeys } from 'librechat-data-provider';
 
 export const clearDraft = debounce((id?: string | null) => {
   localStorage.removeItem(`${LocalStorageKeys.TEXT_DRAFT}${id ?? ''}`);
 }, 2500);
 
+/** Synchronously removes both text and file drafts for a conversation (or NEW_CONVO fallback) */
+export const clearAllDrafts = (conversationId?: string | null) => {
+  const key = conversationId || Constants.NEW_CONVO;
+  localStorage.removeItem(`${LocalStorageKeys.TEXT_DRAFT}${key}`);
+  localStorage.removeItem(`${LocalStorageKeys.FILES_DRAFT}${key}`);
+};
+
 export const encodeBase64 = (plainText: string): string => {
   try {
     const textBytes = new TextEncoder().encode(plainText);