More informative output when exporting tickets

[bschmalhofer]

When exporting ticket we currently get messages like:

---

Exporting chunk 653...
Success: 1101 succeeded
Error: 0 failed.
File Export_20240920a/issue_12_000653.csv saved.

But the count of 1101 successes is actually 100 tickets and 100*10 = 1000 articles. Nor sure why an extra success is counted. Anyways, it would be nice to see the details.

[bschmalhofer]

Also, as the final output a summation over all chunks would be nice.