LLM chat assistant for the data and dashboard system

We need add an-LLM driven assistant to our product which is an information system with dashboard and filters. Basic core functionality: it should take user's question, formulate a query to the database or run a document search, retrieve data, send for final processing and return the answer. It needs to maintain context for conversations of reasonable length (15-20 prompts). Platform: web only. Adding mobile will the next project. Support functionality: pre-set/contextual questions, saving chat history, billing for different pricing models. Integration: connect it with the production system built with TypeScript/Next.js, Supabase. Please reply providing 2 numbers: - Your total estimate of a budget for this work - Duration in weeks