Add Docker Compose for quick local dashboard setup

[Cubiczan]

Make it one-command to spin up AgentForge dashboard locally.

What to do:

• Create docker-compose.yml with dashboard backend + optional local DB
• Create Dockerfile for the dashboard
• Update README with Docker quick start section

Getting started:

• See dashboard/app.py for the FastAPI backend
• Dashboard is pure Python + React (served as static template)

Tags: good first issue