Do not consider a field that is not of type "attachment > image" as one to be used to capture photos

Nobody has claimed this yet.

I noticed that in QGIS project properties > Mergin Maps all fields set as "attachment" are shown as they are to be used for photos, even the ones that are not of type "image" (i.e. also the fields set as "No content"), and for those fields in Mergin Maps App the widget to take/choose photos is shown (so I guess this report is also about the mobile App).

This seems to me at least very inconvenient as there is a clear use for attachment fields that are not photos, like the ones that for example store a PDF file relative path that must be opened within the Mergin Maps app with the methods described in docs:

seems right now is not possible to use the same project (under Mergin Maps control) on Desktop to edit/add features and associate them a PDF file (because if the used field uses the attachment widget it will always renders with the photo capture widget on mobile), and then with an HTML widget allow to open it on mobile. I can't only think about some workaround, but maybe I'm wrong(?).

Start by tracing how the QGIS plugin identifies attachment fields and how the mobile app selects the photo widget. Verify the behavior for attachment fields of type image versus fields with No content, and confirm that non-image attachments can still be opened through the documented HTML widget flow.

Written by the indexing model from the issue text.