- Renamed MYSQL_ROOT_PASSWORD to DB_ROOT_PASSWORD and MYSQL_PASSWORD to DB_PASSWORD for consistent naming
- Updated docker-compose.yml to map DB_* variables to MySQL container's expected MYSQL_* format
- Removed redundant DATABASE_URL variable since individual DB_* variables are now used
- Added default values for DB_USER, DB_NAME, DB_HOST, and DB_PORT in docker-compose.yml
- Updated all documentation files to reference new standar
