feat(ui): design token discipline, accessibility and i18n pass

- Replace all hardcoded Color literals outside lib/tema with theme tokens (new static brand palette in PluriWaveTokens); media notification uses the brand color instead of the Material default purple
- Favorite button on station cards grows to a 48dp target and becomes an independent semantics node for screen readers (Semantics container fix)
- All flutter_animate call sites route through the PluriAnimate reduced-motion gate (zero direct .animate() left)
- Locale-aware short dates via intl DateFormat (new lib/l10n/formato_fechas.dart) replacing the hardcoded DD/MM/YYYY; proper plural messages for the favorites counter; example stream URL as a localized key - all 13 locales
- Rounded shimmer placeholders matching card radii; shimmer loading state in search instead of a bare spinner; rounded icon variants unified in settings; bottom-sheet conventions on the custom station form
- Fix latent debug crash: vacation editor read AppLocalizations in initState
- 11 new tests (121 total green), flutter analyze clean

lib/pantallas/pantalla_inicio.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_animate/flutter_animate.dart';
 import 'package:provider/provider.dart';
 import 'package:shimmer/shimmer.dart' as shimmer;
 
@@ -7,6 +6,7 @@ import '../estado/estado_busqueda.dart';
 import '../estado/estado_radio.dart';
 import '../l10n/gen/app_localizations.dart';
 import '../modelos/emisora.dart';
+import '../tema/pluri_animate.dart';
 import '../widgets/pluri_glass_surface.dart';
 import '../widgets/pluri_icon.dart';
 import '../widgets/pluri_layout.dart';
@@ -230,7 +230,10 @@ class _PantallaInicioState extends State<PantallaInicio> {
                             ),
                             label: Text(e.nombre, maxLines: 1),
                             onPressed: () => reproducirMinimizado(context, e),
-                          ).animate().fadeIn(delay: (i * 50).ms);
+                          ).pluriFadeIn(
+                            context,
+                            delay: Duration(milliseconds: i * 50),
+                          );
                         },
                       ),
             ),
@@ -354,7 +357,11 @@ class _PantallaInicioState extends State<PantallaInicio> {
         (context, i) => TarjetaEmisora(
           emisora: emisoras[i],
           onTap: () => reproducirMinimizado(context, emisoras[i]),
-        ).animate().fadeIn(delay: (i * 30).ms).slideY(begin: 0.1),
+        ).pluriFadeSlideIn(
+          context,
+          delay: Duration(milliseconds: i * 30),
+          beginY: 0.1,
+        ),
         childCount: emisoras.length,
       ),
       gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(