feat: implement NIP-77 negentropy sync for historical data

Replace EOSE-based sync completion with negentropy reconciliation for:
- Initial connect (fresh sync)
- Daily sync (Layer 1 announcements)
- Stale reconnect (>15 min)

Key changes:
- Add NegentropySyncResult struct with remote_only, local_only, received fields
- Add supports_negentropy() using try-and-fallback approach
- Add negentropy_sync_filter() using nostr-sdk client.sync() API
- Modify handle_connect_or_reconnect() to use negentropy for fresh/stale sync
- Modify daily_sync() to use negentropy for Layer 1
- Single-warning logging per relay when negentropy fails

Quick reconnects (<15 min) unchanged - still use REQ with since filter.
If negentropy unsupported, gracefully falls back to REQ+EOSE flow.

0 files changed, 0 insertions, 0 deletions