add pvc-autoresizer for automatic PVC expansion before volumes fill up [ci skip]

Deploy topolvm/pvc-autoresizer controller that monitors kubelet_volume_stats
via Prometheus and auto-expands annotated PVCs. Annotated all 9 block-storage
PVCs (proxmox-lvm) with per-PVC thresholds and max limits. Updated PVFillingUp
alert to critical/10m (means auto-expansion failed) and added PVAutoExpanding
info alert at 80%.

stacks/monitoring/modules/monitoring/prometheus.tf

@@ -4,6 +4,11 @@ resource "kubernetes_persistent_volume_claim" "prometheus_server_pvc" {
   metadata {
     name      = "prometheus-data-proxmox"
     namespace = kubernetes_namespace.monitoring.metadata[0].name
+    annotations = {
+      "resize.topolvm.io/threshold"     = "90%"
+      "resize.topolvm.io/increase"      = "10%"
+      "resize.topolvm.io/storage_limit" = "500Gi"
+    }
   }
 
   spec {