feat(update-scripts): replace whiptail with msg_menu for unattended updates

Remove all whiptail dialogs from ct update_script() functions and replace
with msg_menu() - a lightweight read-based menu that supports:
- PHS_SILENT=1: auto-selects first (default) option for unattended mode
- Interactive: numbered menu with 10s timeout and default fallback

Converted scripts (whiptail menu → msg_menu):
- plex.sh, npmplus.sh, cronicle.sh, meilisearch.sh, node-red.sh
- homeassistant.sh, podman-homeassistant.sh
- vaultwarden.sh, alpine-vaultwarden.sh
- loki.sh, alpine-loki.sh
- alpine-grafana.sh, alpine-redis.sh, alpine-valkey.sh
- alpine-nextcloud.sh

Simplified scripts (removed unnecessary whiptail for single-action updates):
- alpine.sh, alpine-docker.sh, alpine-zigbee2mqtt.sh

Special handling:
- gitea-mirror.sh: replaced yesno/msgbox with read -rp confirmations,
  exit 75 in silent mode for major version upgrades requiring interaction
- vaultwarden.sh/alpine-vaultwarden.sh: passwordbox replaced with
  read -r -s -p, skipped in silent mode with warning
- nginxproxymanager.sh: exit 1 → exit 75 for disabled script

Infrastructure:
- Added msg_menu() helper to misc/build.func
- Added exit code 75 handling in update-apps.sh (skip, not fail)

Closes #11620

tools/pve/update-apps.sh

@@ -421,6 +421,8 @@ for container in $CHOICE; do
 
   if [ $exit_code -eq 0 ]; then
     msg_ok "Updated container $container"
+  elif [ $exit_code -eq 75 ]; then
+    echo -e "${YW}[WARN]${CL} Container $container skipped (requires interactive mode)"
   elif [ "$BACKUP_CHOICE" == "yes" ]; then
     msg_info "Restoring LXC from backup"
     pct stop $container