Optimize BLE mesh network for robustness and range (#314)

- Fixed relay probability calculation for 2-node networks (0% relay needed)
- Added protocol ACKs to prevent unnecessary retransmissions
- Implemented MessageState for enhanced duplicate detection
- Added exponential backoff for collision avoidance
- Fixed duplicate sends for bidirectional connections
- Resolved packet ID generation issues using immutable fields only
- Implemented smart rate limiting with progressive throttling
- Removed unnecessary debug logging and fixed build warnings
- Optimized message routing to prevent flooding in small networks

Co-authored-by: jack <jackjackbits@users.noreply.github.com>

bitchat/Protocols/BinaryProtocol.swift

@@ -19,11 +19,12 @@ extension Data {
 }
 
 // Binary Protocol Format:
-// Header (Fixed 13 bytes):
+// Header (Fixed 17 bytes):
 // - Version: 1 byte
 // - Type: 1 byte  
 // - TTL: 1 byte
 // - Timestamp: 8 bytes (UInt64)
+// - SequenceNumber: 4 bytes (UInt32)
 // - Flags: 1 byte (bit 0: hasRecipient, bit 1: hasSignature)
 // - PayloadLength: 2 bytes (UInt16)
 //
@@ -34,7 +35,7 @@ extension Data {
 // - Signature: 64 bytes (if hasSignature flag set)
 
 struct BinaryProtocol {
-    static let headerSize = 13
+    static let headerSize = 17
     static let senderIDSize = 8
     static let recipientIDSize = 8
     static let signatureSize = 64
@@ -77,6 +78,11 @@ struct BinaryProtocol {
             data.append(UInt8((packet.timestamp >> (i * 8)) & 0xFF))
         }
         
+        // Sequence number (4 bytes, big-endian)
+        for i in (0..<4).reversed() {
+            data.append(UInt8((packet.sequenceNumber >> (i * 8)) & 0xFF))
+        }
+        
         // Flags
         var flags: UInt8 = 0
         if packet.recipientID != nil {
@@ -165,6 +171,13 @@ struct BinaryProtocol {
         }
         offset += 8
         
+        // Sequence number
+        let sequenceData = unpaddedData[offset..<offset+4]
+        let sequenceNumber = sequenceData.reduce(0) { result, byte in
+            (result << 8) | UInt32(byte)
+        }
+        offset += 4
+        
         // Flags
         let flags = unpaddedData[offset]; offset += 1
         let hasRecipient = (flags & Flags.hasRecipient) != 0
@@ -240,7 +253,8 @@ struct BinaryProtocol {
             timestamp: timestamp,
             payload: payload,
             signature: signature,
-            ttl: ttl
+            ttl: ttl,
+            sequenceNumber: sequenceNumber
         )
     }
 }

bitchat/Protocols/BitchatProtocol.swift

@@ -139,8 +139,9 @@ struct BitchatPacket: Codable {
     let payload: Data
     let signature: Data?
     var ttl: UInt8
+    let sequenceNumber: UInt32  // New field for duplicate detection
     
-    init(type: UInt8, senderID: Data, recipientID: Data?, timestamp: UInt64, payload: Data, signature: Data?, ttl: UInt8) {
+    init(type: UInt8, senderID: Data, recipientID: Data?, timestamp: UInt64, payload: Data, signature: Data?, ttl: UInt8, sequenceNumber: UInt32 = 0) {
         self.version = 1
         self.type = type
         self.senderID = senderID
@@ -149,10 +150,11 @@ struct BitchatPacket: Codable {
         self.payload = payload
         self.signature = signature
         self.ttl = ttl
+        self.sequenceNumber = sequenceNumber
     }
     
     // Convenience initializer for new binary format
-    init(type: UInt8, ttl: UInt8, senderID: String, payload: Data) {
+    init(type: UInt8, ttl: UInt8, senderID: String, payload: Data, sequenceNumber: UInt32 = 0) {
         self.version = 1
         self.type = type
         // Convert hex string peer ID to binary data (8 bytes)
@@ -171,6 +173,7 @@ struct BitchatPacket: Codable {
         self.payload = payload
         self.signature = nil
         self.ttl = ttl
+        self.sequenceNumber = sequenceNumber
     }
     
     var data: Data? {