Codex Proxy RS

Deploys PostgreSQL 18, Redis 8 and a single gateway built from waterpen6/codex-proxy-rs. The Zeabur deployment changes must be present on the repository's main branch first. Sign in as admin@cpr.local using the gateway service's Initial admin password instruction. Database credentials are derived from separate platform-generated random seeds. Keep the seeds and persistent volumes when restarting or redeploying. Upgrade by redeploying the Git service; do not use in-container updates.