* feat: split Host Alerts into Host Alerts, Container Alerts, and Stacks guardrails
Move global_crash from Host Alerts to new Monitoring > Container Alerts section.
Move health gate and env deploy guardrails from Host Alerts to
Infrastructure > Stacks > Deploy Guardrails subsection.
Host Alerts now contains only host threshold settings (CPU, RAM, disk,
alert suppression, and the master host_alerts_enabled toggle).
Stacks gains a Deploy Guardrails subsection (node-scoped, admin-gated)
alongside the existing Workflow controls (browser-local).
Dashboard Crash detection row now routes to Container Alerts.
* docs: update crash detection toggle description to match new Container Alerts section
Anso