feat: add VPS Monitor backend and frontend services

- Create systemd service for VPS Monitor agent.
- Add FastAPI backend with endpoints for managing VPS configurations and statuses.
- Implement Dockerfile for backend service with required dependencies.
- Create frontend using React with Vite and Tailwind CSS for styling.
- Add API client for communicating with the backend.
- Implement components for displaying VPS information and logs.
- Set up Docker Compose for orchestrating backend and frontend services.
- Add environment configuration files for backend and agent.
- Implement CORS support in the backend for frontend communication.

vps-monitor/backend/.env.example

@@ -0,0 +1,3 @@
+CONFIG_FILE=data/vps.json
+AGENT_TIMEOUT=5
+CORS_ORIGINS=http://localhost:5173,http://localhost:3000