docs: Update README and fix worker startup instructions

README updates:
- Update docker compose command (now main docker-compose.yml)
- Remove obsolete insecure registries section (MinIO replaces local registry)
- Add .env configuration section for AI agent API keys

Worker management fixes:
- Add worker_service field to API response (backend)
- Fix CLI help message to use correct service name with 'docker compose up -d'
- Use modern 'docker compose' syntax instead of deprecated 'docker-compose'

This ensures users get correct instructions when workers aren't running.

backend/src/api/workflows.py

@@ -567,6 +567,7 @@ async def get_workflow_worker_info(
         "workflow": workflow_name,
         "vertical": vertical,
         "worker_container": f"fuzzforge-worker-{vertical}",
+        "worker_service": f"worker-{vertical}",
         "task_queue": f"{vertical}-queue",
         "required": True
     }