chore: Enable Participating tab for conversations (#11714)

## Summary

This PR enables the **Participating** conversation view in the main
sidebar and keeps the behavior aligned with existing conversation views.

## What changed

- Added **Participating** under Conversations in the new sidebar.
- Added a guard in conversation realtime `addConversation` flow so
generic `conversation.created` events are not injected while the user is
on Participating view.
- Added participating route mapping in conversation-list redirect helper
so list redirects resolve correctly to `/participating/conversations`.

## Scope notes

- Kept changes minimal and consistent with current `develop` behavior.
- No additional update-event filtering was added beyond what existing
views already do.

---------


Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/dashboard/store/modules/conversations/helpers/actionHelpers.js

@@ -30,6 +30,14 @@ export const isOnUnattendedView = ({ route: { name: routeName } }) => {
   return UNATTENDED_ROUTES.includes(routeName);
 };
 
+export const isOnParticipatingView = ({ route: { name: routeName } }) => {
+  const PARTICIPATING_ROUTES = [
+    'conversation_participating',
+    'conversation_through_participating',
+  ];
+  return PARTICIPATING_ROUTES.includes(routeName);
+};
+
 export const isOnFoldersView = ({ route: { name: routeName } }) => {
   const FOLDER_ROUTES = [
     'folder_conversations',