feat: integrate nostrdb relay indexing

- 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>

crates/enostr/src/relay/subs_debug.rs

@@ -229,6 +229,7 @@ fn calculate_error_size(error: &Error) -> usize {
         | Error::InvalidBech32
         | Error::InvalidByteSize
         | Error::InvalidSignature
+        | Error::InvalidRelayUrl
         | Error::Io(_)
         | Error::InvalidPublicKey => mem::size_of_val(error), // No heap usage