Auto dark/bright follows the sun at the tablet's own location

Without a light sensor an app may read (the Redmi Pad SE has none), auto is dark while
the sun is more than 4° below the horizon (lib/theme/sun.dart), at Android's coarse
location, polled and kept across restarts. The tablet's own, not the Orin's GNSS: the
tablet has its own GNSS and cellular. Android's dark theme is the last fallback.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/pages/settings.dart

@@ -65,9 +65,9 @@ class SettingsPage extends StatelessWidget {
                       ? 'now ${lux.toStringAsFixed(lux < 10 ? 1 : 0)} lux; dark at '
                             '${LightSwitch.darkAt.round()} or less, bright from ${LightSwitch.brightAt.round()}'
                       : sun != null
-                      ? 'now ${sun.round()}° above the horizon at the last GNSS position; '
-                            'dark below ${darkBelowDeg.round()}°'
-                      : 'no GNSS position yet';
+                      ? 'the sun is ${sun.abs().round()}° ${sun < 0 ? 'below' : 'above'} the horizon here; '
+                            'dark from ${(-darkBelowDeg).round()}° below'
+                      : 'no location yet';
                   return Text(
                     'Auto follows ${themes.autoSource} ($now). '
                     'The status bar button holds one; a long press there is auto again.',