Filesystem layout (credentials/config)

• /etc/simai-env/sites/<domain>/php.ini — per-site PHP ini overrides (managed by site php-ini-*), mode 0644 root:root.
• /etc/simai-env/sites/<domain>/db.env — per-site database credentials (managed by site db-*), mode 0640 root:root; source of truth for DB_NAME/DB_USER/DB_PASS/DB_HOST/DB_CHARSET/DB_COLLATION.
• Project env files (e.g., <project>/.env) receive DB_* via site db-export or site add/export; written idempotently with env_set_kv.