Setup docs drift: DATABASE_URL, PORT, REDIS_URL missing from CONTRIBUTING.md

Hi — found a concrete contributor onboarding gap while comparing config files against docs:

.env.example:2-56 defines DATABASE_URL, PORT, and REDIS_URL as required — CONTRIBUTING.md:48-83 mentions neither

A new contributor clones the repo, misses these vars, and hits connection failures on first run with no clear pointer to what's missing.

Proposed fix — add to the Environment Setup section in CONTRIBUTING.md:

DATABASE_URL=postgresql://...
PORT=3000
REDIS_URL=redis://localhost:6379

Happy to open a PR if confirmed.