Remove dead code and simplify codebase

- Remove unused BinaryEncodable protocol and BinaryMessageType enum
- Delete MockNoiseSession.swift (never used in tests)
- Remove all relay detection code (hardcoded to false)
  - Removed isRelayConnected property from BitchatPeer
  - Removed relayConnected case from ConnectionState enum
  - Cleaned up relay-related UI indicators in ContentView
  - Removed relay status checks from ChatViewModel
- Simplified peer connection logic by removing relay layer

Total: 169 lines removed across 5 files

bitchat/Protocols/BinaryEncodingUtils.swift

@@ -221,18 +221,3 @@ extension Data {
     }
 }
 
-// MARK: - Binary Message Protocol
-
-protocol BinaryEncodable {
-    func toBinaryData() -> Data
-    static func fromBinaryData(_ data: Data) -> Self?
-}
-
-// MARK: - Message Type Registry
-
-enum BinaryMessageType: UInt8 {
-    case deliveryAck = 0x01
-    case readReceipt = 0x02
-    case noiseIdentityAnnouncement = 0x09
-    case noiseMessage = 0x0A
-}