y.js container hygiene #3105

Initial Checklist

• I understand this is a user story and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

User Story

As an administrator, I want the y.js server container to behave like a production-grade service so that I can operate, monitor and restart it without losing user data.

User Value

Operability, data integrity

Acceptance Criteria

• The image defines a HEALTHCHECK that reflects actual readiness (process up and websocket endpoint reachable)
• A SIGTERM handler shuts down gracefully: stop accepting new connections, persist/flush open documents, close websockets within a documented grace period
• The compose setup declares depends_on with condition: service_healthy where applicable
• Logs go to stdout/stderr
• Restart policy and grace period are documented for administrators (in README.md of the service)