Dockerfile linter — security, best-practices, layer analysis

Send your Dockerfile content — get back a structured JSON audit: issues list with line numbers (security errors, warnings, info); metrics (stages, RUN layer count, multi-stage flag); and a verdict. Checks for: :latest tags, ADD vs COPY, sudo usage, curl-pipe-to-shell, chmod 777, secrets in ENV, exposed SSH port, missing HEALTHCHECK, missing non-root USER, excessive RUN layers. No LLM, no network, deterministic. Input: Dockerfile text string or JSON {"dockerfile": "..."}.