Add deep research history with ability to reopen and continue chats

## Summary Users should be able to view their own deep research history, click on past items to reopen them, see the chat history associated with each item, and continue the conversation from where they left off. ## Steps to Reproduce Not provided. ## Expected Behaviour - A user can see a list of their past deep research sessions. - Clicking a past session opens it and displays the full chat history. - The user can continue the chat from that point. ## Actual Behaviour Not provided. ## Environment Not provided. --- *Reported by **retoor** via DevPlace.*