RTK/GPS Inject screen mockup

Here's a mockup of what the RTK/GPS Inject screen might look like. I think it's easier for people to understand but I leave it to your better judgement of course.

The issue provides only a mockup image and names no files, tests, or entry point. Review the MissionPlanner desktop UI and RTK/GPS injection flow first, then confirm the desired screen and acceptance criteria with maintainers; done is an agreed implementation plan and an accepted screen matching the requirements.

Written by the indexing model from the issue text.