feat: add phpMyAdmin service configuration

[monteshot]

• Add docker-compose.phpmyadmin.yml for phpMyAdmin service
• Update svc.cmd to conditionally include phpMyAdmin configuration
• Ensure phpMyAdmin config file is generated if not present
• Add regeneratePMAConfig function to core.sh
• Call regeneratePMAConfig on env changes in env.cmd
• Include phpMyAdmin as a global service in core.sh