Auto dark/bright takes a light sensor where the device allows one

lib/theme/light.dart: dark at 15 lux or less, bright from 60, held 5 s; Settings shows the
reading. The Redmi Pad SE refuses apps its only light sensor (Xiaomi's, from the front
camera), so there Auto keeps following Android's dark theme. DASH-NEXT.md records the
other lux sources.

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

lib/pages/settings.dart

@@ -7,6 +7,7 @@ import '../actions/server_url.dart';
 import '../link/boundary.dart';
 import '../link/net.dart';
 import '../shell_scope.dart';
+import '../theme/light.dart';
 import '../theme/palette.dart';
 
 class SettingsPage extends StatelessWidget {
@@ -55,9 +56,16 @@ class SettingsPage extends StatelessWidget {
             ListTile(
               leading: Icon(themes.isDark ? Icons.dark_mode : Icons.light_mode),
               title: const Text('Dark or bright'),
-              subtitle: const Text(
-                "Auto follows Android's dark theme and its schedule. "
-                "The Dash's button holds one; a long press there is auto again.",
+              subtitle: ValueListenableBuilder(
+                valueListenable: themes.lux,
+                builder: (context, lux, _) => Text(
+                  lux == null
+                      ? "Auto follows Android's dark theme and its schedule (no light sensor). "
+                            'The status bar button holds one; a long press there is auto again.'
+                      : 'Auto follows the light sensor: dark at ${LightSwitch.darkAt.round()} lux or less, '
+                            'bright from ${LightSwitch.brightAt.round()}; now ${lux.toStringAsFixed(lux < 10 ? 1 : 0)} lux. '
+                            'The status bar button holds one; a long press there is auto again.',
+                ),
               ),
             ),
             Padding(