fix: pass search id to searchbots ask (#15646)

### What problem does this PR solve?
This change ensures `/searchbots/ask` receives `search_id` from the
frontend, so the backend can load the matching search configuration when
the shared search flow invokes the endpoint.

### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/pages/next-search/hooks.ts

@@ -344,6 +344,7 @@ export const useSendQuestion = (
           kb_ids: kbIds,
           question: q,
           tenantId,
+          search_id: searchId,
         });
       }
       testChunk({