Release v0.4.0: full dependency trees for every ecosystem (#77)

Release v0.4.0: full dependency trees for every ecosystem

chore(release): v0.3.0

Correctness release for the SCA engine: dependencies of two ecosystems were
never checked, advisories could land on the wrong package, and the findings that
did come back had no CVE, description, real severity or upgrade target. Also
orders findings by severity in every output, keeps the monitor's token off disk,
and reports secrets on commented-out lines.

No version literal to bump this time — internal/version derives it from the tag.
Only the illustrative JSON samples in README and docs/usage were updated.

fix(ci): grant contents:write to the release job so assets upload

The workflow declares `contents: read` at the top level, so
`softprops/action-gh-release` failed with "Resource not accessible by
integration" and never attached the binaries. Both v0.1.0 and v0.2.0 were
published with zero assets as a result.

Scope the write permission to the release job, leaving every other job with
read-only access to the repository contents.

docs: add CHANGELOG, SECURITY, CODE_OF_CONDUCT and issue/PR templates (…

…#34)

Prepares the project for OWASP project submission and aligns with community
open-source health standards.

- CHANGELOG.md: Keep a Changelog format, documents the 0.1.0 initial release
- SECURITY.md: private vulnerability disclosure policy (GitHub Security
  Advisories + email), supported versions, response SLAs
- CODE_OF_CONDUCT.md: Contributor Covenant 2.1, with enforcement contact
- .github/ISSUE_TEMPLATE: bug report and feature request templates plus a
  config.yml that routes security reports to private advisories (also fixes the
  broken "Bug Report template" reference in CONTRIBUTING.md)
- .github/PULL_REQUEST_TEMPLATE.md: checklist covering tests, gofmt, lint and
  govulncheck
- CONTRIBUTING.md / README.md: link the new Code of Conduct and Security Policy

No code changes.

Co-authored-by: filipi86 <filipi86@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>