feat: iSCSI, Longhorn disk labels, labctl asahi command, ZIP32 fix

k3s host prep:
- Add iSCSI initiator install+enable (Fedora: iscsi-initiator-utils,
  Ubuntu: open-iscsi) — required by Longhorn
- Add Longhorn disk label to k3s server+agent configs
- Add Longhorn disk annotation operation in post-install hardening

CLI:
- Add `labctl provision asahi` command with interactive install guide
- Change default SSH user from "michal" to "lab" in all commands
- Change admin user in bastion progress callback to "lab"

Asahi provisioning fixes:
- Download installer_data.json locally (installer reads it as file)
- Use REPO_BASE to serve upstream ZIP from bastion (LAN speed)
- Fix ZIP32 vs ZIP64: serve original upstream ZIP unmodified
  (our repackaged ZIP used ZIP64 which breaks Asahi urlcache)
- Add /data/asahi-repo fallback path for k3s container PVC mount
- Deploy script syncs asahi-repo to bastion pod after deployment

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

bastion/completions/labctl.bash

@@ -73,6 +73,9 @@ _labctl() {
     "provision register")
       COMPREPLY=($(compgen -W "--role --ip -h --help" -- "$cur"))
       return ;;
+    "provision asahi")
+      COMPREPLY=($(compgen -W "-h --help" -- "$cur"))
+      return ;;
     "provision logs")
       COMPREPLY=($(compgen -W "-f --follow -h --help" -- "$cur"))
       return ;;
@@ -104,7 +107,7 @@ _labctl() {
       COMPREPLY=($(compgen -W "bastion -h --help" -- "$cur"))
       return ;;
     "provision")
-      COMPREPLY=($(compgen -W "list install reprovision debug forget register logs makeiso -h --help" -- "$cur"))
+      COMPREPLY=($(compgen -W "list install reprovision debug forget register asahi logs makeiso -h --help" -- "$cur"))
       return ;;
     "config")
       COMPREPLY=($(compgen -W "list get set path -h --help" -- "$cur"))