feat(android): implement foreground service and notification handling for message synchronization

android/app/src/main/java/com/meshchatx/MeshChatForegroundService.java

@@ -0,0 +1,59 @@
+package com.meshchatx;
+
+import android.app.Notification;
+import android.app.PendingIntent;
+import android.app.Service;
+import android.content.Intent;
+import android.content.pm.ServiceInfo;
+import android.os.Build;
+import android.os.IBinder;
+
+import androidx.annotation.Nullable;
+import androidx.core.app.NotificationCompat;
+
+public class MeshChatForegroundService extends Service {
+    private static final int FG_NOTIFICATION_ID = 0x4d434801;
+
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        Notification notification = buildForegroundNotification();
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            startForeground(
+                FG_NOTIFICATION_ID,
+                notification,
+                ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC
+            );
+        } else {
+            startForeground(FG_NOTIFICATION_ID, notification);
+        }
+        return START_STICKY;
+    }
+
+    private Notification buildForegroundNotification() {
+        PendingIntent pi = PendingIntent.getActivity(
+            this,
+            0,
+            new Intent(this, MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP),
+            PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE
+        );
+        return new NotificationCompat.Builder(this, MeshChatApplication.CHANNEL_ID_BACKGROUND)
+            .setSmallIcon(R.drawable.ic_launcher_foreground)
+            .setContentTitle(getString(R.string.notification_background_title))
+            .setContentText(getString(R.string.notification_background_text))
+            .setOngoing(true)
+            .setContentIntent(pi)
+            .build();
+    }
+
+    @Nullable
+    @Override
+    public IBinder onBind(Intent intent) {
+        return null;
+    }
+
+    @Override
+    public void onDestroy() {
+        stopForeground(STOP_FOREGROUND_REMOVE);
+        super.onDestroy();
+    }
+}