Feature - Extend the Market Trend AI Agent use cases with a new UI and memory integration

I needed to extend the market trend AI agent use case for a customer demo, so would like this new code base to update the current code base for market trend ai agent.
Extends the market-trends-agent use case with LangGraph AgentCore Memory checkpointer and store integration, a React chat UI, and a FastAPI backend proxy — creating a full-stack demo of personalized financial intelligence with persistent broker profiles.

Start by reviewing the existing market-trends-agent use case and identify its current entry points. Then trace how LangGraph AgentCore Memory checkpointer and store integration, the React chat UI, and the FastAPI backend proxy would fit together; done means the demo supports personalized broker profiles with persistent memory.

Written by the indexing model from the issue text.