chore(deploy): rework k8s pipeline, monitoring and postgres 17

Deploy workflow uses git-tracked manifests, DISABLED flag and kustomize overlays; add webinar-checker metrics with ServiceMonitor and alerts; upgrade shared postgres to 17 with statuspage DB and probes/resources.

edu_master/k8s/secrets.yaml.example

@@ -21,6 +21,8 @@ stringData:
   WEBINAR_TELEGRAM_TOKEN: ""
   WEBINAR_ADMIN_ID: ""
   WEBINAR_CHECK_INTERVAL: "60"
+  # Prometheus metrics endpoint (scraped via ServiceMonitor, alerts in k8s/alerts.yaml)
+  METRICS_PORT: "8000"
   # Database
   REDIS_HOST: "redis"
   REDIS_PORT: "6379"