Chore: remove multi_* incompatible fields from NostrEvent model

[rolznz]

Models

• NostrEvent.ReplyId does not support multiple replies per event. I think we should just remove it. It doesn't seem to be used or important for debugging or analytics. I think we can just use the logs
• NostrEvent.State - does not support multiple replies per event, also IMO it is broken because the final state (NOSTR_EVENT_STATE_HANDLER_EXECUTED) overwrites NOSTR_EVENT_STATE_HANDLER_ERROR if the reply is published successfully. I think this should also be removed and just use the logs.
• NostrEvent.RepliedAt - we can use the last reply time here I guess. I think the field is useful.

[im-adithya]

Agreed, I never really used the NostrEvent table as we get good analysis of what's happening from the DataDog logs

[bumi]

as discussed. +1 and we add a replies table in the future.

[im-adithya]

Closing as I opened #231