Fix ubuntu-jammy Docker build: update NodeSource and ENV format

- Replace deprecated apt-key NodeSource setup (node_16.x/focal) with
  modern gpg keyring method using node_20.x/nodistro, fixing GPG
  signature verification failure
- Convert all legacy ENV key value syntax to ENV key=value format
  to eliminate 15 Dockerfile linting warnings

Client: build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Generated-by: Claude Sonnet 4.6
1 file changed