migrate iSCSI block volumes from democratic-csi to Proxmox CSI [ci skip]

Replace TrueNAS iSCSI (democratic-csi) with Proxmox CSI plugin for all
block storage PVCs. Eliminates double-CoW (ZFS + LVM-thin) and removes
the iSCSI network hop for database I/O.

New stack: stacks/proxmox-csi/ — deploys proxmox-csi-plugin Helm chart
with StorageClass "proxmox-lvm" using existing local-lvm thin pool.

Migrated PVCs (12 total):
- Phase 1 standalone: plotting-book, novelapp, vaultwarden, nextcloud, prometheus
- Phase 2 StatefulSets: CNPG PostgreSQL (2), MySQL InnoDB (3), Redis (2)

All services verified healthy post-migration.

stacks/proxmox-csi/main.tf

@@ -0,0 +1,16 @@
+variable "nfs_server" { type = string }
+
+data "vault_kv_secret_v2" "secrets" {
+  mount = "secret"
+  name  = "viktor"
+}
+
+module "proxmox-csi" {
+  source               = "./modules/proxmox-csi"
+  tier                 = local.tiers.cluster
+  proxmox_url          = "https://192.168.1.127:8006/api2/json"
+  proxmox_token_id     = data.vault_kv_secret_v2.secrets.data["proxmox_csi_token_id"]
+  proxmox_token_secret = data.vault_kv_secret_v2.secrets.data["proxmox_csi_token_secret"]
+  proxmox_cluster_name = "pve"
+  kube_config_path     = var.kube_config_path
+}