docs: add Installation, Configuration, recipes, and FAQ Wiki was previously coverage-only. Add operator-facing docs: - Installation (xcaddy, Docker, image tags) - Configuration (every directive, defaults, gotchas) - Recipe: static site (Hugo/Jekyll-style) - Recipe: reverse proxy (capture-and-convert mode) - FAQ (Caddyfile path-matcher gotcha, auth ordering, ETag/gzip, cold-start, 503, sidecar paths, multi-instance, etc.) - Updated Home and Sidebar to surface the new pages Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>