Fix Noise handshake stability and session synchronization issues

- Add peer presence tracking with lastHeardFromPeer to detect reconnections
- Automatically send identity announcement when detecting peer reconnection after 30s
- Clear stale sessions when receiving handshake from recently-seen peer (likely restart)
- Add peers to activePeers when successfully decrypting their messages
- Fix thread safety in handshake coordinator with concurrent collections
- Extend message delivery timeouts (30s→120s private, 60s→180s room, 300s→600s favorite)
- Add per-peer encryption queues to prevent nonce desynchronization
- Make NoiseSession encrypt/decrypt operations thread-safe with barrier flag
- Initialize lastSuccessfulMessageTime when handshake completes
- Send identity announcement when decryption fails to prompt session reset
- Improve handshake state logging and debugging

This fixes:
- Peers stuck in "establishing encryption" after restart
- Nonce desynchronization causing "Decryption failed at nonce N"
- Asymmetric peer visibility (one peer sees the other but not vice versa)
- Thread safety issues causing crashes with pendingPrivateMessages
- Sessions marked as stale immediately after establishment

bitchat/Noise/NoiseProtocol.swift

@@ -299,6 +299,7 @@ class NoiseHandshakeState {
             throw NoiseError.handshakeComplete
         }
         
+        SecureLogger.log("NoiseHandshake[\(role)]: Writing message \(currentPattern + 1)/\(messagePatterns.count)", category: SecureLogger.noise, level: .info)
         
         var messageBuffer = Data()
         let patterns = messagePatterns[currentPattern]
@@ -390,6 +391,7 @@ class NoiseHandshakeState {
             throw NoiseError.handshakeComplete
         }
         
+        SecureLogger.log("NoiseHandshake[\(role)]: Reading message \(currentPattern + 1)/\(messagePatterns.count)", category: SecureLogger.noise, level: .info)
         
         var buffer = message
         let patterns = messagePatterns[currentPattern]