Users were wiped on container recreation because they shared the
backend_data volume with ephemeral pharmacy/medicine data. Postgres
gets its own named volume (postgres_data) that survives deploys.
- Add postgres:16-alpine service + postgres_data volume to compose
- Add pg + connect-pg-simple deps
- userDbGet/userDbRun helpers: PG when PG_URL set, SQLite fallback
- Sessions use connect-pg-simple when pgPool available
- create-admin.js: PG-aware, SQLite fallback for local dev
- push_subscriptions.user_id: plain INTEGER (cross-DB FK dropped)
- Tests unchanged — no PG_URL in test env = SQLite fallback
Set PG_PASSWORD in server .env before next deploy.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Antoni Nuñez Romeu