fix(chrome): rebuild MiniReproductor as a full-bleed opaque bar with art

Item 22 / audit 3.6 (t4:184-188): the mini player was a floating
999-radius glass pill with no artwork. Replace it with a 60px opaque
bar (listSurface at .97 alpha), full-bleed edge to edge, showing the
station's square 42x42 artwork instead of the abstract playing-bars
indicator. app.dart no longer wraps the bar in the balloon nav's own
8px side margin, so it now spans the full width.

MiniReproductor.altura is re-measured (72 -> 60) now that the bar's
content height is fixed by construction; PluriLayout.bottomChromeInset
derives from it as before. Both the S3-R3 configurarLocalizaciones
guard and the altura measurement test still pass unmodified.

test/widgets/pluri_bottom_navigation_test.dart

@@ -194,16 +194,12 @@ void main() {
     semantics.dispose();
   });
 
-  testWidgets('every tab meets the 48x48dp minimum tap target', (
-    tester,
-  ) async {
+  testWidgets('every tab meets the 48x48dp minimum tap target', (tester) async {
     await tester.pumpWidget(hostFor(0));
     await tester.pump();
 
     for (var i = 0; i < items.length; i++) {
-      final size = tester.getSize(
-        find.byKey(PluriBottomNavigation.itemKey(i)),
-      );
+      final size = tester.getSize(find.byKey(PluriBottomNavigation.itemKey(i)));
       expect(size.width, greaterThanOrEqualTo(48));
       expect(size.height, greaterThanOrEqualTo(48));
     }
@@ -248,22 +244,23 @@ void main() {
               bottomNavigationBar: SafeArea(
                 key: chromeKey,
                 top: false,
-                minimum: const EdgeInsets.only(
-                  bottom: PluriLayout.compactGap,
-                ),
-                child: Padding(
-                  padding: const EdgeInsets.fromLTRB(8, 0, 8, 0),
-                  child: Column(
-                    mainAxisSize: MainAxisSize.min,
-                    children: [
-                      const MiniReproductor(),
-                      PluriBottomNavigation(
+                minimum: const EdgeInsets.only(bottom: PluriLayout.compactGap),
+                child: Column(
+                  mainAxisSize: MainAxisSize.min,
+                  children: [
+                    // Mirrors app.dart's real composition: item 22 / audit
+                    // 3.6 made MiniReproductor full-bleed, so only
+                    // PluriBottomNavigation keeps the 8px side margin.
+                    const MiniReproductor(),
+                    Padding(
+                      padding: const EdgeInsets.fromLTRB(8, 0, 8, 0),
+                      child: PluriBottomNavigation(
                         items: items,
                         selectedIndex: 0,
                         onSelected: (_) {},
                       ),
-                    ],
-                  ),
+                    ),
+                  ],
                 ),
               ),
             ),