Adds support for systems that use SysV init (like Asustor NAS) that don't have
systemd, OpenRC, or launchd. The installer now:
- Detects /etc/init.d as a fallback when no other init system is found
- Creates an LSB-compliant init script with start/stop/restart/status
- Uses update-rc.d (Debian) or chkconfig (RHEL) to enable on boot
- Falls back to manual rc.d symlink creation if neither tool is available
- Properly cleans up on uninstall