[x] Add a note "Last backup on xxx. \n Exported a patients, b healings, c payments" (Tap to view) (Persist in datastore)
[x] Add error note on top of backup page for errors in import/export. Suggest to retry (for now). Persist in datastore - Export failure -> Retry; Import failure -> Show reason + retry; (Create enum for failure reason).
Adds basic import/export pipeline (CSV) Closes #46