🧭 fix: Robust 404 Conversation Not Found Redirect (#11853)

* fix: route to new conversation when conversation not found

* Addressed PR feedback

* fix: Robust 404 conversation redirect handling

- Extract `isNotFoundError` utility to `utils/errors.ts` so axios stays
  contained in one place rather than leaking into route/query layers
- Add `initialConvoQuery.isError` to the useEffect dependency array so
  the redirect actually fires when the 404 response arrives after other
  deps have already settled (was the root cause of the blank screen)
- Show a warning toast so users understand why they were redirected
- Add `com_ui_conversation_not_found` i18n key

* fix: Enhance error handling in getResponseStatus function

- Update the getResponseStatus function to ensure it correctly returns the status from error objects only if the status is a number. This improves robustness in error handling by preventing potential type issues.

* fix: Improve conversation not found handling in ChatRoute

- Enhance error handling when a conversation is not found by checking additional conditions before showing a warning toast.
- Update the newConversation function to include model data and preset options, improving user experience during error scenarios.

* fix: Log error details for conversation not found in ChatRoute

- Added logging for the initial conversation query error when a conversation is not found, improving debugging capabilities and error tracking in the ChatRoute component.

---------

Co-authored-by: Dan Lew <daniel@mightyacorn.com>

client/src/routes/ChatRoute.tsx

@@ -1,15 +1,22 @@
 import { useEffect } from 'react';
-import { Spinner } from '@librechat/client';
 import { useParams } from 'react-router-dom';
 import { useRecoilCallback, useRecoilValue } from 'recoil';
+import { Spinner, useToastContext } from '@librechat/client';
 import { Constants, EModelEndpoint } from 'librechat-data-provider';
 import { useGetModelsQuery } from 'librechat-data-provider/react-query';
 import type { TPreset } from 'librechat-data-provider';
+import {
+  useNewConvo,
+  useAppStartup,
+  useAssistantListMap,
+  useIdChangeEffect,
+  useLocalize,
+} from '~/hooks';
 import { useGetConvoIdQuery, useGetStartupConfig, useGetEndpointsQuery } from '~/data-provider';
-import { useNewConvo, useAppStartup, useAssistantListMap, useIdChangeEffect } from '~/hooks';
-import { getDefaultModelSpec, getModelSpecPreset, logger } from '~/utils';
+import { getDefaultModelSpec, getModelSpecPreset, logger, isNotFoundError } from '~/utils';
 import { ToolCallsMapProvider } from '~/Providers';
 import ChatView from '~/components/Chat/ChatView';
+import { NotificationSeverity } from '~/common';
 import useAuthRedirect from './useAuthRedirect';
 import temporaryStore from '~/store/temporary';
 import store from '~/store';
@@ -33,6 +40,8 @@ export default function ChatRoute() {
   useIdChangeEffect(conversationId);
   const { hasSetConversation, conversation } = store.useCreateConversationAtom(index);
   const { newConversation } = useNewConvo();
+  const { showToast } = useToastContext();
+  const localize = useLocalize();
 
   const modelsQuery = useGetModelsQuery({
     enabled: isAuthenticated,
@@ -92,6 +101,29 @@ export default function ChatRoute() {
         keepLatestMessage: true,
       });
       hasSetConversation.current = true;
+    } else if (
+      conversationId &&
+      endpointsQuery.data &&
+      modelsQuery.data &&
+      initialConvoQuery.isError &&
+      isNotFoundError(initialConvoQuery.error)
+    ) {
+      const result = getDefaultModelSpec(startupConfig);
+      const spec = result?.default ?? result?.last;
+      showToast({
+        message: localize('com_ui_conversation_not_found'),
+        severity: NotificationSeverity.WARNING,
+      });
+      logger.log(
+        'conversation',
+        'ChatRoute initialConvoQuery isNotFoundError',
+        initialConvoQuery.error,
+      );
+      newConversation({
+        modelsData: modelsQuery.data,
+        ...(spec ? { preset: getModelSpecPreset(spec) } : {}),
+      });
+      hasSetConversation.current = true;
     } else if (
       conversationId === Constants.NEW_CONVO &&
       assistantListMap[EModelEndpoint.assistants] &&
@@ -125,6 +157,7 @@ export default function ChatRoute() {
     roles,
     startupConfig,
     initialConvoQuery.data,
+    initialConvoQuery.isError,
     endpointsQuery.data,
     modelsQuery.data,
     assistantListMap,