RewriteEngine On
RewriteCond %{DOCUMENT_ROOT}/backend/dist-frontend/$1 -f
RewriteRule ^(.*)$ dist-frontend/$1 [L]
RewriteCond %{THE_REQUEST} \s/backend/dist-frontend/ [NC,OR]
RewriteCond $1 !^dist-frontend/
RewriteRule ^(.*)$ router.php [L]