infra(cloud-init): deliver baseline via bpg user-data snippet; drop netplan/meta-data templates

bpg/proxmox generates cloud-init network-config (static IP/gw/DNS) and
meta-data natively from the VM initialization block, so remove
network-config.yaml.tftpl and meta-data.yaml.tftpl. The rich first-boot
baseline (users, SSH key, packages, kernel modules, Longhorn /dev/vdb
mount, swap-off) is preserved and shipped as a user-data snippet
referenced by initialization.user_data_file_id. Comments updated
(libvirt -> Proxmox); /dev/vdb still valid (data disk is virtio1).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

infra/cloud-init/user-data.yaml.tftpl

@@ -18,7 +18,7 @@ users:
     ssh_authorized_keys:
       - ${ssh_authorized_key}
 
-# Baseline packages: guest agent (tofu/libvirt), and Longhorn's node prerequisites
+# Baseline packages: guest agent (tofu/Proxmox), and Longhorn's node prerequisites
 # (open-iscsi provides iscsid + iscsiadm; nfs-common provides the NFS client).
 package_update: true
 packages:
@@ -48,8 +48,8 @@ write_files:
       fs.inotify.max_user_instances       = 8192
       fs.inotify.max_user_watches         = 524288
 
-# Dedicated Longhorn data disk (/dev/vdb) → ext4 mounted at /var/lib/longhorn.
-# nofail so a node still boots if the disk is absent during a rebuild.
+# Dedicated Longhorn data disk (/dev/vdb, the VM's virtio1 disk) → ext4 mounted at
+# /var/lib/longhorn. nofail so a node still boots if the disk is absent during a rebuild.
 fs_setup:
   - label: longhorn
     filesystem: ext4
@@ -65,7 +65,7 @@ runcmd:
   - ["modprobe", "br_netfilter"]
   - ["modprobe", "iscsi_tcp"]
   - ["sysctl", "--system"]
-  # Longhorn needs iscsid running; guest agent for libvirt/tofu.
+  # Longhorn needs iscsid running; guest agent for Proxmox/tofu.
   - ["systemctl", "enable", "--now", "iscsid"]
   - ["systemctl", "enable", "--now", "qemu-guest-agent"]
   # k3s/kubelet baseline: disable swap.