fix(favoritos,grabaciones): replace glass cards with flat rows

Item 23 / audit 4.3, 12.4 (t4:226-232, 616-619): Favoritos and
Grabaciones rows were full glass cards / ListTiles with two stacked
buttons and no artwork slot. Replace with flat, background-less rows
via a new shared FilaEmisoraPlana widget (square art, name+meta, a
circular play affordance) plus a bespoke Grabaciones row (44x12
placeholder art -- recordings carry no per-station favicon, so this
is a themed fallback, not invented artwork).

Favoritos keeps "Move to list" / "Remove from favorites" behind an
overflow menu (same underlying methods, unchanged) instead of two
always-visible buttons, since dropping either would be a functional
regression the prototype's own row doesn't have to solve for.

Also 12.1 (t4:610): the Grabaciones header action is folder_open, not
a generic gear.

test/pantallas/pantalla_grabaciones_test.dart

@@ -8,6 +8,7 @@ import 'package:pluriwave/l10n/gen/app_localizations.dart';
 import 'package:pluriwave/modelos/archivo_grabacion.dart';
 import 'package:pluriwave/pantallas/pantalla_grabaciones.dart';
 import 'package:pluriwave/servicios/servicio_grabacion_radio.dart';
+import 'package:pluriwave/widgets/pluri_glass_surface.dart';
 import 'package:pluriwave/widgets/pluri_push_scaffold.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
@@ -137,7 +138,9 @@ void main() {
       );
       await pumpStable(tester);
 
-      await tester.tap(find.byIcon(Icons.settings_outlined));
+      // Audit 12.1 (t4:610): the header action icon is `folder_open`, not
+      // a generic gear.
+      await tester.tap(find.byIcon(Icons.folder_open_rounded));
       await pumpStable(tester);
 
       expect(find.byType(PluriPushScaffold), findsNWidgets(2));
@@ -194,6 +197,51 @@ void main() {
     expect(find.byIcon(Icons.play_circle_fill_rounded), findsNWidgets(3));
   });
 
+  // Item 23 / audit 12.4 (t4:616-619): flat, background-less rows with a
+  // 44x44/radius-12 thumbnail placeholder -- replacing the PluriGlassSurface
+  // + ListTile card, which had no artwork slot at all.
+  testWidgets(
+    'rows are flat -- no ListTile, no per-row PluriGlassSurface -- with a '
+    '44x44/radius-12 thumbnail placeholder',
+    (tester) async {
+      final estado = EstadoGrabacion(
+        servicio: _FakeServicioGrabacionConArchivos([
+          fijaA,
+          fijaB,
+        ], maxBytesFijo: 200 * 1024 * 1024),
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(
+        buildScreen(
+          estado: estado,
+          reproductor: _ReproductorGrabacionesFake(const {}),
+        ),
+      );
+      await pumpStable(tester);
+
+      expect(
+        find.byType(ListTile),
+        findsNothing,
+        reason: 'audit 12.4 replaces the ListTile row with a flat Row',
+      );
+      expect(
+        find.byType(PluriGlassSurface),
+        findsOneWidget,
+        reason: 'only the storage card keeps a surface -- rows do not',
+      );
+
+      final miniaturas = find.byKey(const ValueKey('fila-grabacion-arte'));
+      expect(miniaturas, findsNWidgets(2));
+      expect(tester.getSize(miniaturas.first), const Size(44, 44));
+      final clip = tester.widget<ClipRRect>(miniaturas.first);
+      expect(
+        (clip.borderRadius as BorderRadius).topLeft,
+        const Radius.circular(12),
+      );
+    },
+  );
+
   testWidgets('15.2-B: empty folder renders an empty state, not an error', (
     tester,
   ) async {