Firehose

• Change loopback.ts module to firehose.ts.
• Adds a relays table. The firehose uses all relays.
• Autodiscover new relays from events through the firehose.
• Add a script to populate relays from an API (deno task relays:sync https://api.nostr.watch/v1/online).

TODO:

• Limit the number of relays per host (add an indexed host column).
• Add an active column to relays and only pull active ones.

Maybe?

• Refactor pool into a separate module, shared between the firehose and client.