- Upgrade `nostrdb` to v0.6.1 with relay metadata support
- Switch to `nostr::RelayUrl` for typed relay URLs
- Use `process_event_with()` to pass relay info during ingestion
- Update `Relay`, `RelayPool`, and unknown ID logic accordingly
This enables richer indexing with relay provenance in events.
Signed-off-by: William Casarin <jb55@jb55.com>