feat(material): adopt expressive controls across the app

lib/theme/app_theme.dart

@@ -7,8 +7,7 @@ import 'package:spotiflac_android/theme/app_tokens.dart';
 class AppTheme {
   static const Color defaultSeedColor = Color(kDefaultSeedColor);
 
-  /// Component radii resolve from the same tokens the widgets read, so the
-  /// scale cannot drift between `ThemeData` and hand-built containers.
+  /// Shared surfaces use one radius scale; actions use round Material shapes.
   static const AppTokens _tokens = AppTokens.standard;
 
   // Override Flutter's default page transitions. Recent Flutter defaults the
@@ -148,9 +147,7 @@ class AppTheme {
       ElevatedButtonThemeData(
         style: ElevatedButton.styleFrom(
           elevation: 1,
-          shape: RoundedRectangleBorder(
-            borderRadius: BorderRadius.circular(_tokens.radiusControl),
-          ),
+          shape: const StadiumBorder(),
           padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
         ),
       );
@@ -158,9 +155,7 @@ class AppTheme {
   static FilledButtonThemeData _filledButtonTheme(ColorScheme scheme) =>
       FilledButtonThemeData(
         style: FilledButton.styleFrom(
-          shape: RoundedRectangleBorder(
-            borderRadius: BorderRadius.circular(_tokens.radiusControl),
-          ),
+          shape: const StadiumBorder(),
           padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
         ),
       );
@@ -168,9 +163,7 @@ class AppTheme {
   static OutlinedButtonThemeData _outlinedButtonTheme(ColorScheme scheme) =>
       OutlinedButtonThemeData(
         style: OutlinedButton.styleFrom(
-          shape: RoundedRectangleBorder(
-            borderRadius: BorderRadius.circular(_tokens.radiusControl),
-          ),
+          shape: const StadiumBorder(),
           padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
         ),
       );

lib/theme/material_expressive.dart

@@ -0,0 +1,132 @@
+import 'package:flutter/material.dart';
+import 'package:material_3_expressive/material_3_expressive.dart';
+import 'package:material_ui/material_ui.dart' as material_ui;
+import 'package:spotiflac_android/theme/mornye_theme.dart';
+
+/// Motion-heavy expressive controls use their static Material counterpart when
+/// the OS requests reduced motion. Mornye owns its own component system.
+bool materialExpressiveEnabled(BuildContext context) =>
+    !context.isMornye && !MediaQuery.disableAnimationsOf(context);
+
+/// Bridges the app's Flutter theme to the separate Material UI widget library.
+/// Local artwork colors, dynamic colors, fonts and AMOLED surfaces stay intact.
+class MaterialExpressiveScope extends StatelessWidget {
+  const MaterialExpressiveScope({super.key, required this.child});
+
+  final Widget child;
+  static final _themes = Expando<material_ui.ThemeData>();
+  static final _expressiveThemes = Expando<M3EThemeData>();
+
+  static material_ui.ThemeData _adapt(ThemeData theme) {
+    final cached = _themes[theme];
+    if (cached != null) return cached;
+    final c = theme.colorScheme;
+    final t = theme.textTheme;
+    final adapted = material_ui.ThemeData(
+      brightness: theme.brightness,
+      platform: theme.platform,
+      useMaterial3: true,
+      scaffoldBackgroundColor: theme.scaffoldBackgroundColor,
+      colorScheme: material_ui.ColorScheme(
+        brightness: c.brightness,
+        primary: c.primary,
+        onPrimary: c.onPrimary,
+        primaryContainer: c.primaryContainer,
+        onPrimaryContainer: c.onPrimaryContainer,
+        primaryFixed: c.primaryFixed,
+        primaryFixedDim: c.primaryFixedDim,
+        onPrimaryFixed: c.onPrimaryFixed,
+        onPrimaryFixedVariant: c.onPrimaryFixedVariant,
+        secondary: c.secondary,
+        onSecondary: c.onSecondary,
+        secondaryContainer: c.secondaryContainer,
+        onSecondaryContainer: c.onSecondaryContainer,
+        secondaryFixed: c.secondaryFixed,
+        secondaryFixedDim: c.secondaryFixedDim,
+        onSecondaryFixed: c.onSecondaryFixed,
+        onSecondaryFixedVariant: c.onSecondaryFixedVariant,
+        tertiary: c.tertiary,
+        onTertiary: c.onTertiary,
+        tertiaryContainer: c.tertiaryContainer,
+        onTertiaryContainer: c.onTertiaryContainer,
+        tertiaryFixed: c.tertiaryFixed,
+        tertiaryFixedDim: c.tertiaryFixedDim,
+        onTertiaryFixed: c.onTertiaryFixed,
+        onTertiaryFixedVariant: c.onTertiaryFixedVariant,
+        error: c.error,
+        onError: c.onError,
+        errorContainer: c.errorContainer,
+        onErrorContainer: c.onErrorContainer,
+        surface: c.surface,
+        onSurface: c.onSurface,
+        onSurfaceVariant: c.onSurfaceVariant,
+        surfaceDim: c.surfaceDim,
+        surfaceBright: c.surfaceBright,
+        surfaceContainerLowest: c.surfaceContainerLowest,
+        surfaceContainerLow: c.surfaceContainerLow,
+        surfaceContainer: c.surfaceContainer,
+        surfaceContainerHigh: c.surfaceContainerHigh,
+        surfaceContainerHighest: c.surfaceContainerHighest,
+        outline: c.outline,
+        outlineVariant: c.outlineVariant,
+        inverseSurface: c.inverseSurface,
+        onInverseSurface: c.onInverseSurface,
+        inversePrimary: c.inversePrimary,
+        shadow: c.shadow,
+        scrim: c.scrim,
+        surfaceTint: c.surfaceTint,
+      ),
+      textTheme: material_ui.TextTheme(
+        displayLarge: t.displayLarge,
+        displayMedium: t.displayMedium,
+        displaySmall: t.displaySmall,
+        headlineLarge: t.headlineLarge,
+        headlineMedium: t.headlineMedium,
+        headlineSmall: t.headlineSmall,
+        titleLarge: t.titleLarge,
+        titleMedium: t.titleMedium,
+        titleSmall: t.titleSmall,
+        bodyLarge: t.bodyLarge,
+        bodyMedium: t.bodyMedium,
+        bodySmall: t.bodySmall,
+        labelLarge: t.labelLarge,
+        labelMedium: t.labelMedium,
+        labelSmall: t.labelSmall,
+      ),
+    );
+    _themes[theme] = adapted;
+    return adapted;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = _adapt(Theme.of(context));
+    final expressive = _expressiveThemes[theme] ??=
+        M3EThemeData.fromMaterial(theme).copyWith(
+          fontFamily: theme.textTheme.bodyMedium?.fontFamily,
+          navigationBarTheme: const M3ENavigationBarTheme(heightMedium: 72),
+        );
+    final content = M3ETheme(
+      data: expressive,
+      // M3E's projection omits fixed color roles. Keep the complete host theme
+      // nearest the widgets so it also retains AMOLED and platform typography.
+      child: material_ui.Theme(data: theme, child: child),
+    );
+    if (Localizations.of<material_ui.MaterialLocalizations>(
+          context,
+          material_ui.MaterialLocalizations,
+        ) !=
+        null) {
+      return content;
+    }
+    // Also support isolated sheets/previews hosted by a Flutter MaterialApp.
+    return Localizations.override(
+      context: context,
+      delegates: const [material_ui.GlobalMaterialLocalizations.delegate],
+      child: Directionality(
+        textDirection: Directionality.of(context),
+        child: content,
+      ),
+    );
+  }
+}