Improve setup and developer onboarding documentation

[wJubran]

Overview

The current README covers installation but lacks detailed troubleshooting, Windows/Mac/Linux-specific notes, and a clear developer onboarding guide for new contributors.

What Needs Improvement

1. Setup Troubleshooting Guide

• Common errors when installing Python dependencies
• MetaTrader5 package installation issues on non-Windows systems
• Port conflicts with the FastAPI server
• Electron packaging issues

2. Platform-Specific Notes

• Windows (primary supported platform)
• macOS (MT5 not natively supported — workarounds)
• Linux (headless or WSL setup)

3. Developer Quickstart

• Step-by-step guide for new contributors to get the project running locally in under 10 minutes
• How to run backend only (without Electron)
• How to test WebSocket connection manually
• How to add a new provider from scratch

4. Architecture Diagram

• Visual diagram showing how backend, Electron shell, and frontend communicate
• Data flow: broker -> provider -> data_server.py -> WebSocket -> UI

Deliverable

• Expanded README sections or separate docs in a docs/ directory
• An architecture diagram (can be ASCII or an image)

Skills Needed

Technical writing, Markdown, basic understanding of Python/FastAPI/WebSocket