Change of sync interval reverts to default ("Once a day") after app close and re-open

[sunkup]

Confirmed bug

1. Change the interval to something that is not "Once a day" and tap "OK"
2. Close the app and reopen it
3. Open the set interval view and see the setting has been reverted

Discussed in #436

^{Originally posted by sniff-numeral September 27, 2024}
Hello,
As the title says. When I change the sync interval to something other than the default, the button reverts back to daily when I close and re-open the app. However, while the button is on daily, the app syncs at the previously selected interval (I only tested 15 minutes though). So the problem seems to be cosmetic.