Frosted bottom bar: adjustable blur and opacity with Less/Default/More presets

Settings > Appearance shows a preset control plus Blur and Opacity sliders
(new NooSlider) while frosted glass is on; values persist and feed
NooBottomBar.frostedBlur/frostedOpacity. Default matches the old fixed look.

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

test/providers/settings_frosted_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:noo/providers/settings_controller.dart';
+
+/// The frosted-glass bottom bar's blur/opacity settings and their presets.
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() => SharedPreferences.setMockInitialValues({}));
+
+  Future<SettingsController> build() async {
+    final settings = SettingsController();
+    // `_load` is async and not exposed; one event-loop turn lets it finish.
+    await Future<void>.delayed(Duration.zero);
+    return settings;
+  }
+
+  test('starts on the Default preset', () async {
+    final settings = await build();
+    expect(settings.frostedPreset, FrostedGlassPreset.standard);
+    expect(settings.bottomBarFrostedBlur, 20);
+    expect(settings.bottomBarFrostedOpacity, 0.72);
+  });
+
+  test('presets set both values and are recognised again', () async {
+    final settings = await build();
+    for (final preset in FrostedGlassPreset.values) {
+      settings.setFrostedPreset(preset);
+      expect(settings.bottomBarFrostedBlur, preset.blur);
+      expect(settings.bottomBarFrostedOpacity, preset.opacity);
+      expect(settings.frostedPreset, preset);
+    }
+  });
+
+  test('presets run from lighter to stronger frosting', () {
+    expect(
+      FrostedGlassPreset.less.blur,
+      lessThan(FrostedGlassPreset.standard.blur),
+    );
+    expect(
+      FrostedGlassPreset.standard.blur,
+      lessThan(FrostedGlassPreset.more.blur),
+    );
+    expect(
+      FrostedGlassPreset.less.opacity,
+      greaterThan(FrostedGlassPreset.standard.opacity),
+    );
+    expect(
+      FrostedGlassPreset.standard.opacity,
+      greaterThan(FrostedGlassPreset.more.opacity),
+    );
+  });
+
+  test('moving a slider off every preset leaves none selected', () async {
+    final settings = await build();
+    settings.setFrostedBlur(27);
+    expect(settings.frostedPreset, isNull);
+    settings.setFrostedBlur(FrostedGlassPreset.standard.blur);
+    expect(settings.frostedPreset, FrostedGlassPreset.standard);
+  });
+
+  test('values are clamped to their ranges', () async {
+    final settings = await build();
+    settings
+      ..setFrostedBlur(500)
+      ..setFrostedOpacity(0);
+    expect(settings.bottomBarFrostedBlur, maxFrostedBlur);
+    expect(settings.bottomBarFrostedOpacity, minFrostedOpacity);
+    settings
+      ..setFrostedBlur(-3)
+      ..setFrostedOpacity(9);
+    expect(settings.bottomBarFrostedBlur, minFrostedBlur);
+    expect(settings.bottomBarFrostedOpacity, maxFrostedOpacity);
+  });
+
+  test('saved values are restored (and clamped) on the next launch', () async {
+    SharedPreferences.setMockInitialValues({
+      'ui_bottom_bar_frosted_blur': 32.0,
+      'ui_bottom_bar_frosted_opacity': 7.0,
+    });
+    final settings = await build();
+    expect(settings.bottomBarFrostedBlur, 32);
+    expect(settings.bottomBarFrostedOpacity, maxFrostedOpacity);
+  });
+}