Add Docker health check and graceful shutdown

[xmaks82]

Description

Add health check to docker-compose.yml and handle SIGTERM/SIGINT gracefully in the CLI.

Implementation

1. Add healthcheck to docker-compose.yml (e.g., check if process is running)
2. Handle SIGTERM in CLI for graceful shutdown (save state, close connections)
3. Add `stop_grace_period` to docker-compose.yml