chore: bump @e4a/pg-js to 1.8.0

[dobby-coder]

Closes #100

Bumps @e4a/pg-js from 1.7.1 to 1.8.0 (own org package; pulls latest postguard-js release).

Verification

• npm install @e4a/pg-js@1.8.0 --save-dev — clean install, 0 vulnerabilities.
• npm run docs:build — succeeds in ~10.8s.
• No test script in this repo.

Reviewer quickstart

git fetch origin && git checkout chore/bump-pg-js-1.8.0 && npm install && npm run docs:build

[dobby-coder]

Self-review (cannot approve own PR):

• npm install: clean, 0 vulnerabilities
• npm run docs:build: succeeds in ~8.3s
• CI: build + Conventional Commit both green

Pure devDependency bump of an own-org package. No source changes. LGTM.