v0.1.13 — automated npm publishing

Added

• ledgerly is published to npm — pnpm add ledgerly /
  npm install ledgerly now installs the engine and server. (v0.1.12
  was the first release, hand-published; from v0.1.13 on, publishing
  is automated — see below.)
• Automated npm publishing. release.yml now publishes the npm
  package on every v* tag push, alongside the existing GHCR image
  job. It runs npm publish --provenance, so the package carries a
  Sigstore-signed build-provenance attestation — the same supply-chain
  guarantee the container images already have. The npm job is
  push-only: npm rejects republishing an existing version, so a
  workflow_dispatch image re-run skips it.
• package.json metadata for a complete npm listing — license
  (Apache-2.0), repository, homepage, bugs, keywords,
  author — plus CHANGELOG.md in the published files and a
  prepublishOnly gate (typecheck + lint + test + build) so a broken
  or stale build can't be published.
• docs/cross-currency-payouts.md — design notes for the deferred
  cross-currency payout accounting: the analysis, the recommended
  journal-entry shape, and the exact Stripe payload to capture when
  reporting one.

Fixed

• bin path no longer carries a ./ prefix
  ("ledgerly-server": "dist/server/cli.js") — npm flagged the
  prefixed form at publish time. The published v0.1.12 bin still works
  (npm auto-corrected it); v0.1.13 onward publishes warning-free.

Changed

• README Quick start restructured to lead with docker pull (the
  install path that always works) and to reflect the now-published
  npm package.