Fix request sync duplicate public messages (#707)

Co-authored-by: CC <cc@ggg.local>

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

@@ -7,6 +7,7 @@ import com.bitchat.android.model.IdentityAnnouncement
 import com.bitchat.android.model.RoutedPacket
 import com.bitchat.android.protocol.BitchatPacket
 import com.bitchat.android.protocol.MessageType
+import com.bitchat.android.sync.PacketIdUtil
 import com.bitchat.android.util.toHexString
 import kotlinx.coroutines.*
 import java.util.*
@@ -400,7 +401,7 @@ class MessageHandler(private val myPeerID: String, private val appContext: andro
                 }
                 val savedPath = com.bitchat.android.features.file.FileUtils.saveIncomingFile(appContext, file)
                 val message = BitchatMessage(
-                    id = java.util.UUID.randomUUID().toString().uppercase(),
+                    id = PacketIdUtil.computeIdHex(packet).uppercase(),
                     sender = delegate?.getPeerNickname(peerID) ?: "unknown",
                     content = savedPath,
                     type = com.bitchat.android.features.file.FileUtils.messageTypeForMime(file.mimeType),
@@ -416,6 +417,7 @@ class MessageHandler(private val myPeerID: String, private val appContext: andro
 
             // Fallback: plain text
             val message = BitchatMessage(
+                id = PacketIdUtil.computeIdHex(packet).uppercase(),
                 sender = delegate?.getPeerNickname(peerID) ?: "unknown",
                 content = String(packet.payload, Charsets.UTF_8),
                 senderPeerID = peerID,