Add guard to drop oversized BLE notification assemblies

bitchat/Services/BLEService.swift

@@ -15,6 +15,12 @@ struct NotificationStreamAssembler {
 
         buffer.append(chunk)
 
+        if buffer.count > TransportConfig.bleNotificationAssemblerHardCapBytes {
+            SecureLogger.error("❌ Notification assembler overflow (\(buffer.count) bytes); dropping partial frame", category: .session)
+            buffer.removeAll(keepingCapacity: false)
+            return ([], [], true)
+        }
+
         var frames: [Data] = []
         var dropped: [UInt8] = []
         var reset = false

bitchat/Services/TransportConfig.swift

@@ -30,6 +30,7 @@ enum TransportConfig {
     static let bleDynamicRSSIThresholdDefault: Int = -90
     static let bleConnectionCandidatesMax: Int = 100
     static let blePendingWriteBufferCapBytes: Int = 1_000_000
+    static let bleNotificationAssemblerHardCapBytes: Int = 8 * 1024 * 1024
     static let blePendingNotificationsCapCount: Int = 20
 
     // Nostr