ci: 👷 add ci/cd pipeline - #3

Summary

• Add CI/CD pipelines for multi-arch .deb and .rpm package builds
• Publish packages to APT and YUM/DNF repositories hosted on GitHub Pages
• Modernize debian packaging (debhelper-compat 13, drop upstart/libudev0 deps)
• Add RPM spec file for Rocky Linux / RHEL / Fedora support
• Update README with package installation instructions

CI/CD

• CI (ci.yml): Builds .deb (amd64, arm64, armhf) and .rpm (x86_64, aarch64) on PRs and manual dispatch
• Release (release.yml): Triggered by v* tags — builds all archs, creates GitHub Release, publishes to gh-pages APT/YUM repos at amd989.github.io/mediasmartserverd

Packaging Changes

• debian/control: debhelper-compat 13, dropped libudev0/upstart-job deps
• debian/changelog: bumped to 0.7.0, version overridden from git tag at build time
• debian/postinst, preinst, prerm: systemd-only, removed upstart codepaths
• debian/compat: deleted (replaced by debhelper-compat in control)
• rpm/mediasmartserver.spec: new RPM spec with systemd macros

Test Plan

• Trigger CI manually from Actions tab, verify deb/rpm builds pass on all archs
• Tag v0.7.0, push, verify release workflow creates GitHub Release with artifacts
• Verify gh-pages deploys with APT repo: curl -fsSL .../setup.sh | sudo bash && sudo apt install mediasmartserver
• Verify RPM repo: curl -fsSL .../setup-rpm.sh | sudo bash && sudo dnf install mediasmartserver