phpipam-pfsense-import: every 5min → hourly

Reduces 5-min disk-write spikes on PVE sdc. The cronjob was the
heaviest single contributor in our hourly fan-out investigation
(11.2 MB/s burst when it fired). Kea DDNS still handles real-time
DNS auto-registration; phpIPAM inventory just lags by up to 1h,
which we don't need fresher.

Docs (dns.md, networking.md, .claude/CLAUDE.md) updated to match.

stacks/phpipam/main.tf

@@ -386,7 +386,7 @@ resource "kubernetes_cron_job_v1" "phpipam_pfsense_import" {
     namespace = kubernetes_namespace.phpipam.metadata[0].name
   }
   spec {
-    schedule                      = "*/5 * * * *"
+    schedule                      = "0 * * * *"
     successful_jobs_history_limit = 1
     failed_jobs_history_limit     = 3
     concurrency_policy            = "Forbid"