Implements the full site health auditor with four check groups:
- SSL/TLS (certificate validity, expiry, chain, TLS version, ciphers)
- HTTP (redirect chain, security headers, response time)
- DNS (A/AAAA, MX, SPF, DKIM, DMARC, DNSSEC)
- Infrastructure (CDN detection, common port probes)
Includes CLI with --checks filter, --json and --out flags,
cross-compile Makefile, and GitLab CI pipeline.
Signed-off-by: Blake Ridgway <blake@blakeridgway.com>
