Automatic association of screenshots with string ids

### Describe the problem

I really appreciate the screenshot feature in weblate - it is very helpful to provide critical context for translators. I screenshot new strings in context as I add them to my project.

What is a bit frustrating is that afterwards I have to onto weblate and add the screenshots one by one.

### Describe the solution you would like

If I add a new screenshot to the repository under the path specified screenshot path (e.g. as per project settings / Screenshot file mask ), where the name matches the string id e.g. string_id.png , then automatically associate this screenshot with the string id.

### Describe alternatives you have considered

Adding screenshots manually one by one.

### Screenshots

_No response_

### Additional context

_No response_

Start by tracing how Weblate reads the configured screenshot path or file mask and how uploaded screenshots are associated with strings. The feature is complete when a repository screenshot whose filename matches a string ID is automatically associated with that string, while manual association remains available.

Written by the indexing model from the issue text.