Fix installer bugs: broken root checks, PHP version mismatches, dead paths

- Replace $EUID with $(id -u) for root checks across all bin/*.sh and
  install.sh: dash (Debian's /bin/sh) never sets $EUID, so the check was
  silently broken everywhere.
- lemp.sh: make apt-get upgrade non-interactive (--yes), align the Redis
  PHP module and php-fpm restart with $PHP_VERSION instead of a hardcoded
  8.1, and template the nginx PHP-FPM socket path via a PHP_FPM_SOCK
  placeholder substituted at install time.
- nginx-phpmyadmin.conf: fix docroot to match the actual phpMyAdmin
  symlink location created by lemp.sh.
- mysql-db.sh: inline the root check instead of sourcing the
  nonexistent bin/checkroot.sh.
- webhook.sh: fix chowm typo (chown).
- urbackup.sh: copy the systemd unit from assets/ instead of a relative
  path to a file that doesn't exist in the repo.
- _addUserSite.sh: fix invalid `$var=value` assignment and an empty
  if-block that was a POSIX sh syntax error.

Also carries over pending fixes to deploy-drupal.sh (drush now
invoked via vendor/bin/drush) and gitbarrerepos.sh (comment cleanup).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bin/user.sh

@@ -9,7 +9,7 @@ echo -e '\033[35m
 \033[0m'
 echo -e "\033[35;1mCreate new user (you will be asked a user name and a password) \033[0m"
 
-if [ "$EUID" -ne 0 ]; then
+if [ "$(id -u)" -ne 0 ]; then
   echo "Please run as root"
   exit
 fi