Recent files list deleted files
<!--
See our full bug reporting guidelines at https://inkscape.org/contribute/report-bugs/
Writing a good bug report will ensure we'll be able to help efficiently. 🙂
-->
#### Summary:
<!-- Summarize the issue/suggestion concisely: -->
Recent files present a list of files that have been deleted or moved and are not available.
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- open File/Open Recent menu
#### What happened?
There's bunch of files there that are not available.
#### What should have happened?
Show only files that are present.
#### Version info
```
Inkscape 1.5-dev (485b9c5791, 2024-05-30, custom)
```
The recent decision not to check if files are present was the right one from the performance point of view.
But we need a way to trim the list of recent documents to those that can actually be loaded. How and when to do that is to be determined. Ideally, off the main thread, so we are not locking the app UI.
issue