AI-powered Sales Agent Email Generator MCP Server

[la4gia]

This PR delivers the first full version of the Sales Agent Email Generator project.

Key features include:

FastMCP tool server exposing multiple sales agent tools. Streamlit frontend (sales_ui.py) providing a chat-based UI for a Sales Manager workflow. LangChain + LangGraph integration with Google Generative AI (gemini-2.5-flash-preview-05-20) for orchestration.

[ed-donner]

Hey! this is cool, but I'd prefer not to change the uv dependencies for the whole repo as we'd need to do some thorough testing. Please instead update your community_contributions code to ask people to do a uv add for the langchain dependencies you're adding. many thanks