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/webhook.sh

@@ -93,7 +93,7 @@ git --git-dir=/home/"$user"/git-repositories/"$_domain.git" remote add origin "$
 cp -f "$_assets"/webhook-deploy.sh /home/"$user"/webhook-deploy-"$_id".sh
 sed -i -r "s/DOMAIN/$_domain/g" /home/"$user"/webhook-deploy-"$_id".sh
 sed -i -r "s/USER/$user/g" /home/"$user"/webhook-deploy-"$_id".sh
-chowm $user:$user /home/"$user"/webhook-deploy-"$_id".sh
+chown $user:$user /home/"$user"/webhook-deploy-"$_id".sh
 chmod +x /home/"$user"/webhook-deploy-"$_id".sh
 
 # remove git bare repos hook