Two locations with the same id look identical once selected

Location ids are not unique (see the locations.json contract). The picker rows tell them apart by elevation, but after #51 the trigger shows only the id. So pick one of two "DUP9" entries and you can't tell which one is loaded. Add elevation to the trigger, same as the rows.

---
User story: [F2 Identify the location of each SD card's images](https://github.com/CulverLab/sparcd-requirements/wiki/User-Stories#story-f2--identify-the-location-of-each-sd-cards-images)

Start by tracing the picker rows and trigger changed by #51, using the locations.json contract to confirm that elevation distinguishes duplicate ids. Update the trigger to show elevation like the rows, then verify that selecting either DUP9 entry makes the loaded location identifiable.

Written by the indexing model from the issue text.