resilience improvements: MySQL anti-affinity comment, descheduler 5min, prometheus termination 60s

- MySQL InnoDB: keep required anti-affinity but document why (2/3 members OK during node loss)
- Descheduler: increase frequency from hourly to every 5 min for faster rebalancing
- Prometheus: set terminationGracePeriodSeconds=60 to prevent drain timeout [ci skip]

stacks/descheduler/values.yaml

@@ -52,7 +52,7 @@ namespaceOverride: ""
 commonLabels: {}
 
 cronJobApiVersion: "batch/v1"
-schedule: "0 * * * *"
+schedule: "*/5 * * * *"
 suspend: false
 # startingDeadlineSeconds: 200
 successfulJobsHistoryLimit: 10