Rewrite database export

[keunes]

Checklist

• [x ] I have used the search function to see if someone else has already submitted the same feature request.
• [ x] I will only create one feature request per issue.
• [x ] I will describe the problem with as much detail as possible.

System info

App version: 2.2.0-beta3

App source: Google Play

Feature description

Problem you may be having, or feature you want:

We disabled WriteAheadLogging (WAL) for the database at some point because it breaks database exports.

Suggested solution:

Maybe we should write another way to export the database (using proper sqlite to copy the database instead of just copying the file) and re-enable WAL. If anyone is up for rewriting the backup feature, that would be greatly appreciated :)

Both quotes from #2463 (comment)

Screenshots / Drawings / Technical details: