chore: ruff format after mypy fixes

Security hardening: SSRF validation, XSS escapes, rate limiting, proxy default 127.0.0.1, path traversal, webhook validation, security headers

Add Nova-Rules patterns: malware keywords, policy puppetry, Claude triggers, scareware, weaponized code (10 categories total)

Initial release: Palisade Scanner v0.1.0 — web content security for AI agents