Add configurable Docker stop grace period for services

EasyPanel currently appears to recreate Docker Swarm services with Spec.TaskTemplate.ContainerSpec.StopGracePeriod set to 10s, and manual changes made with docker service update --stop-grace-period 120s ... are reset on EasyPanel redeploy/restart.

A concrete use case is Minecraft servers. On shutdown, the container needs enough time for the server process to save worlds, flush player/plugin data, and exit cleanly. With only 10 seconds, Docker may kill the container before graceful shutdown completes, which can cause world rollback, data loss, or duplication issues.

It would be useful to expose a service-level setting equivalent to:

docker service update --stop-grace-period 120s <service>

Ideally this would be configurable per service in Advanced Settings and persisted across redeploys.