fix: CI workflow failing - missing setup steps and dependencies

[sam1064max]

Problem

CI workflow fails: missing Node.js setup, Python setup, test dependencies, and DB service.

Issues

1. No Python version setup - runs default (may not be 3.12)
2. No Node.js setup for frontend lint/test
3. Backend tests run without installing requirements.txt
4. No PostgreSQL service for integration tests
5. Ruff may not resolve imports without installed deps
6. Frontend tests without npm ci first

Expected

All jobs (lint, test, build) pass green.

[sam1064max]

Fixed in #2 - merged to develop.