Remind user to setup and execute backups

### Problem

Most average users I know like for example parents and grandparents of my friends at some point lose some or all of their data because they don’t have an offline backup

### Proposal

Display a notification every now and then when there is no proper backup software configured for the currently logged in user.

Ubuntu already does this. They use deja-dup as backup software if I remember correctly. The same software should also work nicely with wirh elementaryos abd should be installed with elementary by default

### Prior Art (Optional)

_No response_