core: frontend: vehicle-setup: compass calibration issues

... there are some other small compass page issues ... :

- [ ] The Pixhawk only has one listed compass, but still shows an arrow for compass 2, just set pointing north
- it should be hidden if there is no compass for it
- possibly related to #2772?
- [x] The "Compass Learn" dropdown description has a typo where it says "...then _driver_ the vehicle around" (should be _drive_), and is missing the final period
- [x] The "Compass Learn" popup window has the large vehicle calibration title
- [x] The second word in the "Compass Learn" popup description is unnecessarily capitalised ("A Valid position" should be "A valid position")
- [ ] The "Large Vehicle Calibration" popup is using the "Compass Learn" popup's description
- [ ] There's no "back" / "undo" option when you select to enter custom coordinates in the "Large Vehicle Calibration" popup, so to use the GeoIP coordinates from that point you need to either refresh the whole page or copy them from the section above
- It might make more sense to not have the two buttons at all, and just start with the custom coordinates view but pre-filled with the GeoIP coordinates, so the user can either click "use these coordinates" straight away, or change them first if they want custom ones
- To make it extra obvious we could change the confirmation button text to be "Use GeoIP coordinates" when the input coords match the GeoIP ones, and then change it to "Confirm custom coordinates" when they don't match
- [x] The background of all the compass calibration popup window title bars is hardcoded to the light-mode grey

_Originally posted by @ES-Alexander in https://github.com/bluerobotics/BlueOS/issues/2759#issuecomment-2196162798_