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/gitbarrerepos.sh

@@ -110,10 +110,10 @@ if [ "$vh" = "yes" ]; then
   cd /home/"$user"/git-repositories/"$_domain".git/hooks/
   chmod +x post-receive # pre-receive
 
-  # setup git repo on site folder
+  echo "setup git repo on site folder"
   cd /home/"$user"/www/"$_domain"/public_html
   su -c "git init" $user
-  # link to the bare repo
+  echo "link to the bare repo"
   su -c "git remote add origin /home/$user/git-repositories/$_domain.git" $user
   chown -R "$user":"$user" /home/"$user"/www/"$_domain"