Create a relay-pool-backed OutboxRouter.
Relay pool, NIP-65 loader, fallback relays, and optional signer / verifier / relay gate / timeout.
An OutboxRouter for createOutboxService.
If relayPool, loadRelayLists, or fallbackRelays are missing.
relayPool
loadRelayLists
fallbackRelays
Create a relay-pool-backed OutboxRouter.