pnpm v10 is now the npm "latest" tag but generates a different lockfile
format than v9.0 used in this repo, causing --frozen-lockfile to fail.
Replace corepack pnpm@latest with npm install -g pnpm@9 in api and web
Dockerfiles. Also bump docker/* actions to v3/v6 to resolve Node.js 20
deprecation warnings ahead of the June 2026 forced migration.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
