migrate Nextcloud data volume from NFS to iSCSI for fsync support

SQLite on NFS caused persistent 500 errors on WebDAV PROPFIND due to
missing fsync guarantees and database locking under concurrent access.
iSCSI (ext4) provides proper fsync and block-level I/O.

- Replace nfs_volume module with iscsi-truenas PVC (20Gi)
- Update Helm chart to use nextcloud-data-iscsi claim
- Excluded 12.5GB nextcloud.log and corrupted DB from migration

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stacks/nextcloud/chart_values.yaml

@@ -58,10 +58,10 @@ externalDatabase:
 
 persistence:
   enabled: true
-  existingClaim: nextcloud-data
+  existingClaim: nextcloud-data-iscsi
 
   accessMode: ReadWriteOnce
-  size: 100Gi
+  size: 20Gi
 
 startupProbe:
   enabled: true

stacks/nextcloud/main.tf

@@ -122,13 +122,20 @@ resource "kubernetes_config_map" "apache_tuning" {
 #   }
 # }
 
-module "nfs_nextcloud_data" {
-  source     = "../../modules/kubernetes/nfs_volume"
-  name       = "nextcloud-data"
-  namespace  = kubernetes_namespace.nextcloud.metadata[0].name
-  nfs_server = var.nfs_server
-  nfs_path   = "/mnt/main/nextcloud"
-  storage    = "100Gi"
+resource "kubernetes_persistent_volume_claim" "nextcloud_data_iscsi" {
+  metadata {
+    name      = "nextcloud-data-iscsi"
+    namespace = kubernetes_namespace.nextcloud.metadata[0].name
+  }
+  spec {
+    access_modes       = ["ReadWriteOnce"]
+    storage_class_name = "iscsi-truenas"
+    resources {
+      requests = {
+        storage = "20Gi"
+      }
+    }
+  }
 }
 
 module "nfs_nextcloud_backup" {