Add Live Event Consent (kind:30316) to NIP-53

[patrickulrich]

Summary

Adds kind:30316 Live Event Consent to provide a standardized, discoverable mechanism for participants to publish their agreement to join Live Events.

Problem

Currently, NIP-53 defines a proof mechanism where event organizers can include cryptographic proofs in p tags to show participant consent. However, there's no standardized way for:

• Participants to publish their consent proactively
• Event organizers to discover consent events

This requires out-of-band coordination between organizers and participants.

Solution

This PR introduces kind:30316 Live Event Consent events that:

• Allow participants to publish their consent to Nostr relays
• Are discoverable by event organizers via a tag queries
• Use the same cryptographic proof as the existing p tag mechanism

Implementation Notes

• Fully backward compatible - existing proof mechanism still works
• Event organizers can discover consents by querying: {"kinds": [30316], "tags": {"a": ["30311:organizer_pubkey:event_d_tag"]}}
• The proof field uses the same signed SHA256 format already defined in NIP-53