[ci skip] Reduce healthcheck frequency to 8h, fix apiserver audit duplication bug

Change cluster-healthcheck CronJob from every 30min to every 8h.
Replace fragile sed-based audit config in apiserver manifest with
idempotent Python script that deduplicates by name/mountPath,
preventing the duplicate volume entries that crashed the API server.

stacks/openclaw/main.tf

@@ -539,7 +539,7 @@ resource "kubernetes_cron_job_v1" "cluster_healthcheck" {
     }
   }
   spec {
-    schedule                      = "*/30 * * * *"
+    schedule                      = "0 */8 * * *"
     concurrency_policy            = "Forbid"
     failed_jobs_history_limit     = 3
     successful_jobs_history_limit = 3