* 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
Move the browser-local Deploy progress, Progress style, and Diff preview
before save controls out of Appearance into a new Stacks section under the
Infrastructure group. These are stack lifecycle and editor workflow
preferences, not visual style, so Settings now groups them where operators
expect to find them.
Add a browser-local masthead scope so these localStorage-backed sections read
SCOPE browser instead of the misleading global, and apply it to both
Appearance and Stacks. Control behavior, storage keys, and backing hooks are
unchanged; this is an information-architecture move only.
Anso