Value map/relation field: support multi-line descriptions

[tomasMizera]

Summary

Currently, long description values in value map or value relation fields are truncated in the selection dialog. There is no way to add line breaks, forcing users to shorten their descriptions to avoid cut-off text.

Expected behaviour

Descriptions should:

• support line breaks so multi-line text wraps

• expand the list item height to accommodate longer text without truncation.

• Let's introduce a max limit of 3 lines (instead of the current 1)

Current behaviour

Long description strings are cut off with an ellipsis (…) in the value map picker dialog. No workaround exists within the app — users must shorten their descriptions.

Steps to reproduce

1. Create a value map field in a QGIS project with long description strings.
2. Open the feature form in the mobile app and tap the value map field.
3. Observe that descriptions are truncated.