Phase 28b: native location services for Windows + Linux

The cross-platform location story before this was: macOS used CoreLocation, Windows used IP geolocation, Linux used "open a dialog and let the user type their lat/long". The first one was great; the other two were embarrassing. Windows now uses Windows.Devices.Geolocation.Geolocator via WinRT bindings (the Tauri Rust crate windows-rs makes this manageable). Linux uses geoclue2 over D-Bus. Both ask…