fix(ui): align track play button hitboxes

lib/widgets/preview_button.dart

@@ -42,27 +42,21 @@ class PreviewButton extends ConsumerWidget {
     final mainItem = ref.watch(currentMediaItemProvider).value;
     if (_isCurrentMainTrack(mainItem)) {
       final isPlaying = ref.watch(playbackPlayingProvider);
-      return Transform.translate(
-        offset: const Offset(18, 0),
-        child: IconButton(
-          iconSize: size,
-          padding: EdgeInsets.zero,
-          alignment: Alignment.centerRight,
-          visualDensity: VisualDensity.compact,
-          constraints: const BoxConstraints(minWidth: 48, minHeight: 48),
-          icon: Icon(
-            isPlaying
-                ? Icons.pause_circle_filled_rounded
-                : Icons.play_circle_fill_rounded,
-            color: colorScheme.primary,
-          ),
-          tooltip: isPlaying
-              ? context.l10n.previewStop
-              : context.l10n.previewPlay,
-          onPressed: () => ref
-              .read(musicPlayerControllerProvider)
-              .togglePlayPause(isPlaying),
+      return IconButton(
+        iconSize: size,
+        padding: EdgeInsets.zero,
+        constraints: const BoxConstraints(minWidth: 48, minHeight: 48),
+        icon: Icon(
+          isPlaying
+              ? Icons.pause_circle_filled_rounded
+              : Icons.play_circle_fill_rounded,
+          color: colorScheme.primary,
         ),
+        tooltip: isPlaying
+            ? context.l10n.previewStop
+            : context.l10n.previewPlay,
+        onPressed: () =>
+            ref.read(musicPlayerControllerProvider).togglePlayPause(isPlaying),
       );
     }
 
@@ -106,18 +100,13 @@ class PreviewButton extends ConsumerWidget {
         break;
     }
 
-    return Transform.translate(
-      offset: const Offset(18, 0),
-      child: IconButton(
-        iconSize: size,
-        padding: EdgeInsets.zero,
-        alignment: Alignment.centerRight,
-        visualDensity: VisualDensity.compact,
-        constraints: const BoxConstraints(minWidth: 48, minHeight: 48),
-        icon: icon,
-        tooltip: tooltip,
-        onPressed: () => _onPressed(context, ref),
-      ),
+    return IconButton(
+      iconSize: size,
+      padding: EdgeInsets.zero,
+      constraints: const BoxConstraints(minWidth: 48, minHeight: 48),
+      icon: icon,
+      tooltip: tooltip,
+      onPressed: () => _onPressed(context, ref),
     );
   }
 }

test/preview_button_layout_test.dart

@@ -0,0 +1,69 @@
+import 'package:audio_service/audio_service.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/l10n/l10n.dart';
+import 'package:spotiflac_android/models/track.dart';
+import 'package:spotiflac_android/providers/music_player_provider.dart';
+import 'package:spotiflac_android/widgets/preview_button.dart';
+
+void main() {
+  const track = Track(
+    id: 'track-1',
+    name: 'Track',
+    artistName: 'Artist',
+    albumName: 'Album',
+    previewUrl: 'https://example.com/preview.mp3',
+    duration: 180,
+  );
+
+  Future<void> pumpButton(WidgetTester tester, {MediaItem? currentItem}) async {
+    await tester.pumpWidget(
+      ProviderScope(
+        overrides: [
+          currentMediaItemProvider.overrideWith(
+            (ref) => Stream.value(currentItem),
+          ),
+          playbackPlayingProvider.overrideWith((ref) => false),
+        ],
+        child: const MaterialApp(
+          localizationsDelegates: AppLocalizations.localizationsDelegates,
+          supportedLocales: AppLocalizations.supportedLocales,
+          home: Scaffold(body: PreviewButton(track: track)),
+        ),
+      ),
+    );
+    await tester.pump();
+  }
+
+  void expectCenteredHitbox(WidgetTester tester, IconData iconData) {
+    final button = find.byType(IconButton);
+    final icon = find.byIcon(iconData);
+    final hitbox = tester.getRect(button);
+
+    expect(hitbox.width, greaterThanOrEqualTo(48));
+    expect(hitbox.height, greaterThanOrEqualTo(48));
+    expect(tester.getCenter(icon), hitbox.center);
+  }
+
+  testWidgets('preview icon is centered inside its 48dp hitbox', (
+    tester,
+  ) async {
+    await pumpButton(tester);
+    expectCenteredHitbox(tester, Icons.play_circle_outline_rounded);
+  });
+
+  testWidgets('current-track play icon uses the same centered hitbox', (
+    tester,
+  ) async {
+    await pumpButton(
+      tester,
+      currentItem: const MediaItem(
+        id: 'track-1',
+        title: 'Track',
+        artist: 'Artist',
+      ),
+    );
+    expectCenteredHitbox(tester, Icons.play_circle_fill_rounded);
+  });
+}