C2(deploy-infra-alerting): finalize rewrite cards as historical docs

Remove all Mikado frontmatter (status, branch, requires) from chain
cards. Add changelog fragment.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/changelog.d/mikado-deploy-infra-alerting.feature.md

@@ -0,0 +1 @@
+Deploy infrastructure alerting pipeline using Grafana Unified Alerting with ntfy push notifications. 7 alert rules with runbooks covering service health, pod readiness, PostgreSQL, textfile freshness, Frigate cameras, and ArgoCD sync status. services-check now queries the alerting API for covered checks.

docs/how-to/alerts/deploy-infra-alerting.md

@@ -1,10 +1,6 @@
 ---
 title: Deploy Infrastructure Alerting Pipeline
 modified: 2026-03-22
-status: active
-branch: mikado/deploy-infra-alerting
-requires:
-  - refactor-services-check-to-query-alerts
 tags:
   - how-to
   - alerting

docs/how-to/alerts/first-alert-and-runbook.md

@@ -1,8 +1,6 @@
 ---
 title: First Alert and Runbook
 modified: 2026-03-22
-requires:
-  - configure-grafana-alerting-pipeline
 tags:
   - how-to
   - alerting

docs/how-to/alerts/port-services-check-alerts.md

@@ -1,8 +1,6 @@
 ---
 title: Port services-check Alerts to Grafana
 modified: 2026-03-22
-requires:
-  - first-alert-and-runbook
 tags:
   - how-to
   - alerting

docs/how-to/alerts/refactor-services-check-to-query-alerts.md

@@ -1,8 +1,6 @@
 ---
 title: Refactor services-check to Query Alerts
 modified: 2026-03-22
-requires:
-  - port-services-check-alerts
 tags:
   - how-to
   - alerting