The new DB_MAX_CONNECTIONS / DB_ACQUIRE_TIMEOUT_SECS knobs were read by the
backend but never added to .env.example or docker-compose.yml, so an operator
setting them in .env would see no effect (caught by the config meta-tests).
Document both in .env.example and wire them into backend.environment.
Bump to 0.124.8.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>