feat: add ConnectivityReceiver for network state monitoring

android/app/src/main/kotlin/com/traccar/traccar_client/network/ConnectivityReceiver.kt

@@ -0,0 +1,32 @@
+package com.traccar.traccar_client.network
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.net.ConnectivityManager
+import android.net.Network
+import android.net.NetworkCapabilities
+
+class ConnectivityReceiver(
+    private val onConnectivityChange: (Boolean) -> Unit
+) : BroadcastReceiver() {
+
+    private var isNetworkAvailable = false
+
+    override fun onReceive(context: Context, intent: Intent) {
+        val newNetworkState = isNetworkAvailable(context)
+        if (newNetworkState != isNetworkAvailable) {
+            isNetworkAvailable = newNetworkState
+            onConnectivityChange(isNetworkAvailable)
+        }
+    }
+
+    companion object {
+        fun isNetworkAvailable(context: Context): Boolean {
+            val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+            val network = connectivityManager.activeNetwork ?: return false
+            val capabilities = connectivityManager.getNetworkCapabilities(network) ?: return false
+            return capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
+        }
+    }
+}