Mantain RetroShare service up

Is needed to find the way of maintain RetroShare-service always alive on background, sharing and/or downloading.

Actually, at least on Android 10, when elRepo.io lose the focus, the service die. We have implemented a restart and re-login system, but this doesn't fix that the file transfer-sharing doesn't work meanwhile the service is down.

Before, we put the service at the same process than the flutter app and seem that Android kill it less (anyway sometimes it kill it). But, when we implemented the backup system, we needed to separate the processes in order to stop RetroShare to get the backup files and then restart it. This process separation seem to cause more crashes than before.

Maybe we have to check the "keep alive notification" flags because the notification disappear when the phone is in "Do not disturb" mode, while others notifications like Telegram FOSS "keep alive notification" doesn't (check how TelegramFOSS call the keep alive notification).