Feature: Backend API for managing LLM and market-data settings via web UI

Feature: Backend API for managing LLM and market-data settings via web UI: a task in LegoFlow-SWE (Harbor dataset). Problem Configuring the large language model provider, its parameters, and optional market data credentials currently requires manually editing a local .env file. Users of the…

The task

**Problem** Configuring the large language model provider, its parameters, and optional market data credentials currently requires manually editing a local `.env` file. Users of the web‑based interface need a dynamic, UI‑driven way to view and update these settings without touching the filesystem.

Part of Lego-X/LegoFlow-SWE.