feat: fix compose.env

compose.env

@@ -1,12 +1,9 @@
 # MySQL/MariaDB Settings
 MYSQL_ROOT_PASSWORD=123456
 MYSQL_DATABASE=maildb
-MYSQL_USER=root
-MYSQL_PASSWORD=123456
 
 # Backend Database Settings
-# These should match the MySQL/MariaDB settings above
 DB_HOST=email-mysql
-DB_USER=${MYSQL_USER}
-DB_PASSWORD=${MYSQL_PASSWORD}
+DB_USER=root
+DB_PASSWORD=${MYSQL_ROOT_PASSWORD}
 DB_NAME=${MYSQL_DATABASE}