Implement Noise XX Handshake Protocol for Direct Messages (#180)

* noise

* works?

* noise

* temporary

* better

* wip: use subnet

* better

* barely working

* werk

* subnet

* fix peer ID

* 8 byte peer ID

* wip noise

* wip fixes for noise

* std lib for noise

* noise handshake one step further

* buffers

* use fork

* fix imports

* simplify counter

* remove trash

* hashing

* no prologue

* nice

* wip, use noise encryption

* peer ID hex

* simplify session manager

* heavy logging

* use singleton

* Fix Noise session race condition with elegant per-peer actor serialization

- Use Kotlin coroutine actors for per-peer packet processing
- Each peer gets dedicated actor that processes packets sequentially
- Eliminates race conditions in session management without complex locking
- Single surgical change in PacketProcessor - minimal, maintainable
- Leverages Kotlin's native concurrency primitives

* decrypt correctly

* iniator works now

* clean code and fix signature to null

* better

* no signature in private message

* small fixes

* refactor ack

* refactor but untested

* messages working

* wip ack

* wip fix ack

* more logging

* pending tracker

* keep pending connections on errors

* less logging

* refactor model

* refactor frombinarydata

* idendityannouncement refactor and update to new binary protocol

* fix keys

* refix keys

* dms work

* revert to mainnet

* do not change bluetooth adapter name

* keep code but uncomment

* clean up comments

* cleanup comments

app/src/main/java/com/bitchat/android/mesh/FragmentManager.kt

@@ -14,7 +14,8 @@ class FragmentManager {
     
     companion object {
         private const val TAG = "FragmentManager"
-        private const val MAX_FRAGMENT_SIZE = 150  // Match iOS/Rust for BLE compatibility (185 byte MTU limit)
+        private const val FRAGMENT_SIZE_THRESHOLD = 512 // 512 bytes
+        private const val MAX_FRAGMENT_SIZE = 500  // Match iOS/Rust for BLE compatibility (185 byte MTU limit)
         private const val FRAGMENT_TIMEOUT = 30000L // 30 seconds
         private const val CLEANUP_INTERVAL = 10000L // 10 seconds
     }
@@ -39,7 +40,7 @@ class FragmentManager {
     fun createFragments(packet: BitchatPacket): List<BitchatPacket> {
         val data = packet.toBinaryData() ?: return emptyList()
         
-        if (data.size <= MAX_FRAGMENT_SIZE) {
+        if (data.size <= FRAGMENT_SIZE_THRESHOLD) {
             return listOf(packet) // No fragmentation needed
         }