fix(ui): unify scroll and improve playback switching

lib/pantallas/pantalla_favoritos.dart

@@ -18,7 +18,8 @@ class PantallaFavoritos extends StatelessWidget {
     final favoritos = estado.listaFavoritos;
 
     if (favoritos.isEmpty) {
-      return const Column(
+      return ListView(
+        padding: EdgeInsets.fromLTRB(0, 0, 0, 124),
         children: [
           PluriScreenHeader(
             title: 'Favoritos',
@@ -29,7 +30,8 @@ class PantallaFavoritos extends StatelessWidget {
               label: 'Coleccion',
             ),
           ),
-          Expanded(
+          SizedBox(
+            height: 320,
             child: PluriEmptyState(
               glyph: PluriIconGlyph.favorites,
               title: 'Sin favoritos aun',
@@ -40,20 +42,22 @@ class PantallaFavoritos extends StatelessWidget {
       );
     }
 
-    return Column(
-      children: [
-        PluriScreenHeader(
-          title: 'Favoritos',
-          subtitle: 'Reordena tu coleccion y deja arriba las radios que mas importan.',
-          glyph: PluriIconGlyph.favorites,
-          trailing: PluriStatusPill(
-            icon: Icons.library_music_rounded,
-            label: '${favoritos.length} guardadas',
+    return CustomScrollView(
+      slivers: [
+        SliverToBoxAdapter(
+          child: PluriScreenHeader(
+            title: 'Favoritos',
+            subtitle: 'Reordena tu coleccion y deja arriba las radios que mas importan.',
+            glyph: PluriIconGlyph.favorites,
+            trailing: PluriStatusPill(
+              icon: Icons.library_music_rounded,
+              label: '${favoritos.length} guardadas',
+            ),
           ),
         ),
-        Expanded(
-          child: ReorderableListView.builder(
-            padding: const EdgeInsets.fromLTRB(12, 4, 12, 122),
+        SliverPadding(
+          padding: const EdgeInsets.fromLTRB(12, 4, 12, 124),
+          sliver: SliverReorderableList(
             proxyDecorator: (child, index, animation) => ScaleTransition(
               scale: Tween<double>(begin: 1, end: 1.03).animate(animation),
               child: child,