fix(monitoring): remove legacy container and default empty cronJob

The swarm migration in 3848fa9c0 dropped the container.remove({force:true})
that the standalone deploy path used to run. Swarm tasks are named
dokploy-monitoring.<slot>.<id>, so there is no name collision and the
pre-v0.30.0 container survives every redeploy. It also stays pinned to an
orphaned image ID once pullRemoteImage moves the latest tag, so neither a
pull nor a Save clears it and it restarts forever.

Cloud setup spread metricsConfig straight from the row, shipping
cronJob: "" to the agent. robfig/cron rejects an empty spec, so the Go
binary exits before Fiber binds 4500 and Docker restarts it every ~60s.

- remove the legacy container in deployMonitoringService, which covers both
  setupMonitoring and setupWebMonitoring. Cleanup is best effort: a failure
  is logged and the deploy continues, matching the pre-migration behaviour
- default cronJob when configuring monitoring for cloud
- on build servers, clean up the legacy container but deploy no service.
  They never join the swarm, yet cloud setup did create the standalone
  container there before v0.30.0, and the monitoring form has always been
  hidden for them, so those agents are all stuck with an empty cronJob
- cover the above with real-docker tests