Per mara's review of #1718: this env block only exists when hyperhive is
enabled (it lives inside `config = mkIf cfg.enable`), so the
`if hyperhive.enable then gateway else loopback` branch was dead — the
loopback fallback could never be reached. Set HIVE_FORGE_URL to the
gateway vhost directly.
HIVE_MATRIX_URL drops the same redundant `hyperhive.enable` term but
keeps the gatewayHost null-guard — that one is a real fallback for a
domain-less config, not the dead enable branch.
e8c2ef087c