Option to manually enter the 12 seeds at phoenixd startup

[dataresilience]

Thank you for a great solution!!! In order to reduce longer term exposure of the seed words sitting as clear text on disk forever, may I suggest an option where at start of the phoenixd (for the first time) the user get to view, write down and secure the words outside the system and then the words are removed (or never stored) on/from disk once the program is running and at the time of a future restart/reboot of the server (the system will likely know it is not the first time it is started) allowing the words to be manually re-entered? The private key will of course likely be kept in RAM for the duration of the running program but this change would at least mitigate the risk of a disk scanner getting hold of its private parts after a compromised server, as well as not giving them away when the server is not running. Possible? What say you? I think this should be the default way. Could be like a choice -saveseedsondisk to force the existing/current behaviour. Thank you!