feat: save onion addresses to file and .env on host

- entrypoint.sh: background process writes onion-hosts.txt with SSH_ONION and ADMIN_ONION
- docker-compose.yml: bind mount tor-proxy/hosts for onion address persistence on host
- tor-proxy/get-onions.sh: reads onion addresses and updates .env with ADMIN_URL, SSH_ONION, ADMIN_ONION
- .gitignore: exclude tor-proxy/hosts/onion-hosts.txt (secret)
- tor-proxy/hosts/.gitkeep: ensure directory exists in git

docker-compose.yml

@@ -42,6 +42,7 @@ services:
       ADMIN_PORT: ${ADMIN_PORT:-3001}
     volumes:
       - tor_data:/var/lib/tor
+      - ./tor-proxy/hosts:/onion-hosts
     extra_hosts:
       - "host.docker.internal:host-gateway"
     networks: