[ci skip] iSCSI migration, healthcheck fixes, health probes, etcd backup

- Migrate MySQL/PostgreSQL storage from local-path to iscsi-truenas
- Add democratic-csi iSCSI driver module for TrueNAS
- Add open-iscsi to cloud-init VM template
- Fix Shlink health probe path (/api/v3 -> /rest/v3 for Shlink 5.0)
- Fix etcd backup: use etcd 3.5.21-0 (3.6.x is distroless, no /bin/sh)
- Fix cluster healthcheck CronJob: always exit 0 to prevent circular
  JobFailed alerts (reporting via Slack, not exit codes)
- Fix Uptime Kuma nested list handling in cluster-health.sh
- Add health probes to: audiobookshelf, immich ML, ntfy, headscale,
  uptime-kuma, vaultwarden, rybbit (clickhouse + server + client),
  shlink, shlink-web
- Add iSCSI storage documentation to CLAUDE.md

stacks/platform/modules/iscsi-csi/main.tf

@@ -0,0 +1,102 @@
+resource "kubernetes_namespace" "iscsi_csi" {
+  metadata {
+    name = "iscsi-csi"
+    labels = {
+      tier = var.tier
+    }
+  }
+}
+
+resource "helm_release" "democratic_csi" {
+  namespace        = kubernetes_namespace.iscsi_csi.metadata[0].name
+  create_namespace = false
+  name             = "democratic-csi-iscsi"
+  atomic           = true
+  timeout          = 300
+
+  repository = "https://democratic-csi.github.io/charts/"
+  chart      = "democratic-csi"
+
+  values = [yamlencode({
+    csiDriver = {
+      name = "org.democratic-csi.iscsi"
+    }
+
+    storageClasses = [{
+      name                 = "iscsi-truenas"
+      defaultClass         = false
+      reclaimPolicy        = "Retain"
+      volumeBindingMode    = "Immediate"
+      allowVolumeExpansion = true
+      parameters = {
+        fsType = "ext4"
+      }
+      mountOptions = []
+    }]
+
+    controller = {
+      driver = {
+        resources = {
+          requests = { cpu = "25m", memory = "64Mi" }
+          limits   = { cpu = "250m", memory = "256Mi" }
+        }
+      }
+    }
+
+    node = {
+      driver = {
+        resources = {
+          requests = { cpu = "25m", memory = "64Mi" }
+          limits   = { cpu = "250m", memory = "256Mi" }
+        }
+      }
+
+      hostPID  = true
+      hostPath = "/lib/modules"
+    }
+
+    driver = {
+      config = {
+        driver = "freenas-iscsi"
+
+        instance_id = "truenas-iscsi"
+
+        httpConnection = {
+          protocol = "http"
+          host     = var.truenas_host
+          port     = 80
+          apiKey   = var.truenas_api_key
+        }
+
+        sshConnection = {
+          host       = var.truenas_host
+          port       = 22
+          username   = "root"
+          privateKey = var.truenas_ssh_private_key
+        }
+
+        zfs = {
+          datasetParentName                  = "main/iscsi"
+          detachedSnapshotsDatasetParentName = "main/iscsi-snaps"
+        }
+
+        iscsi = {
+          targetPortal = "${var.truenas_host}:3260"
+          namePrefix   = "csi-"
+          nameSuffix   = ""
+          targetGroups = [{
+            targetGroupPortalGroup    = 1
+            targetGroupInitiatorGroup = 1
+            targetGroupAuthType       = "None"
+          }]
+          extentInsecureTpc              = true
+          extentXenCompat                = false
+          extentDisablePhysicalBlocksize = true
+          extentBlocksize                = 512
+          extentRpm                      = "SSD"
+          extentAvailThreshold           = 0
+        }
+      }
+    }
+  })]
+}

stacks/platform/modules/iscsi-csi/variables.tf

@@ -0,0 +1,10 @@
+variable "tier" { type = string }
+variable "truenas_host" { type = string }
+variable "truenas_api_key" {
+  type      = string
+  sensitive = true
+}
+variable "truenas_ssh_private_key" {
+  type      = string
+  sensitive = true
+}