feat: split Host Alerts into Host Alerts, Container Alerts, and Stacks guardrails (#1461)

* 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

frontend/src/components/dashboard/ConfigurationStatus.tsx

@@ -216,7 +216,7 @@ export function ConfigurationStatus({ onOpenSection }: ConfigurationStatusProps
           <Row
             label="Crash detection"
             value={thresholds.globalCrash ? 'On' : 'Off'}
-            onClick={open('host-alerts')}
+            onClick={open('container-alerts')}
           />
         </div>
       </CardContent>

frontend/src/components/dashboard/__tests__/ConfigurationStatus.test.tsx

@@ -1,5 +1,5 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest';
-import { render, screen } from '@testing-library/react';
+import { render, screen, fireEvent } from '@testing-library/react';
 
 const useConfigurationStatusMock = vi.fn();
 vi.mock('../useConfigurationStatus', () => ({
@@ -147,3 +147,18 @@ describe('ConfigurationStatus threshold display', () => {
     expect(badge?.textContent?.trim()).toBe('OFF');
   });
 });
+
+describe('ConfigurationStatus click targets', () => {
+  it('routes Crash detection to container-alerts', () => {
+    const onOpenSection = vi.fn();
+    useConfigurationStatusMock.mockReturnValue({
+      status: makePayload(),
+      loading: false,
+    });
+    render(<ConfigurationStatus onOpenSection={onOpenSection} />);
+    const crashRow = screen.getByText('Crash detection').closest('button');
+    expect(crashRow).toBeDefined();
+    fireEvent.click(crashRow!);
+    expect(onOpenSection).toHaveBeenCalledWith('container-alerts');
+  });
+});