Add Alpine/OpenRC compatibility for init system support
- Updated SPEC.md: Changed systemd requirements to distribution-dependent init system
- Updated ARCHITECTURE.md: Added OpenRC hardening options and init script locations
- Updated build-alpine.sh: Replaced systemd-dev with openrc, use /etc/init.d
- Created configs/linux-patch-api-openrc: Full OpenRC init script
- Added Dockerfile.rpm for RPM build container
Init system support:
- systemd: Debian, Ubuntu, RHEL, CentOS, Fedora
- OpenRC: Alpine Linux
Binary remains init-system agnostic - no Rust code changes required.