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/Services/NoiseEncryptionService.swift

@@ -25,9 +25,9 @@ enum EncryptionStatus: Equatable {
         case .noiseHandshaking:
             return "lock.rotation"
         case .noiseSecured:
-            return "lock"
+            return "lock.fill"  // Changed from "lock" to "lock.fill" for filled lock
         case .noiseVerified:
-            return "lock.shield"
+            return "lock.shield.fill"  // Changed to filled version for consistency
         }
     }