Add public peer mode and improve peer tracking

- Add --public flag for discovery-only peers (no topic message processing)
- Track all topic peers that send messages, not just GossipSub mesh peers
- Distinguish between message author and relay peer in received messages
- Show mesh status (IN MESH/NOT IN MESH) and last seen time for each peer
- Add IP address to all message output
- Use DHT for peer reconnection with cached address fallback
- Improve reconnection timing (2s initial, 10s interval vs 30s)
- Maintain bootstrap connections to keep NAT mappings alive
- Show relay path when messages come through relay peers
- Fix peer tracking to use message author instead of relay peer ID

Author: ordishs