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>

assets/nginx-phpmyadmin.conf

@@ -2,7 +2,7 @@ server {
   listen 80;
   location /phpmyadmin {
     # server_name phpmyadmin.idroot.net;
-    root /var/www/phpmyadmin;
+    root /var/www/html;
 
     index  index.php;
 
@@ -22,7 +22,7 @@ server {
     }
 
     location ~ \.php$ {
-      fastcgi_pass unix:/run/php/php8.2-fpm.sock;
+      fastcgi_pass unix:/run/php/PHP_FPM_SOCK;
       fastcgi_index index.php;
       include fastcgi_params;
       fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;