feat(mvp): PluriWave Fase 1 — estructura completa de la app

- Modelo Emisora: campos completos Radio Browser API (fromApi + fromMap)
- ServicioRadio: cliente Radio Browser API (populares, tendencias, buscar por nombre/país/idioma/tag)
- ServicioAudio: just_audio + audio_service wrapper (play/pause/stop/toggle, fade, background handler)
- ServicioTimer: countdown con fade out gradual (15/30/60/90 min)
- ServicioFavoritos: actualizado a v2 con campos codec/bitrate/votes/clickcount
- EstadoRadio: ChangeNotifier global con Provider
- PantallaInicio: grid emisoras populares, chips género, shimmer loading, pull-to-refresh
- PantallaBuscar: SearchBar + filtros país/idioma, lista resultados
- PantallaFavoritos: ReorderableListView + swipe-to-delete (Dismissible)
- TarjetaEmisora: card + modo compacto ListTile, cached_network_image, shimmer fallback
- MiniReproductor: barra inferior persistente con stream de estado
- app.dart: MaterialApp + Provider + NavigationBar + timer dialog
- main.dart: punto de entrada limpio
- AndroidManifest.xml: permisos INTERNET + FOREGROUND_SERVICE + audio_service receivers

lib/widgets/tarjeta_emisora.dart

@@ -0,0 +1,135 @@
+import 'package:cached_network_image/cached_network_image.dart';
+import 'package:flutter/material.dart';
+import 'package:shimmer/shimmer.dart';
+import '../modelos/emisora.dart';
+
+/// Tarjeta compacta para mostrar una emisora en listas y grids.
+class TarjetaEmisora extends StatelessWidget {
+  final Emisora emisora;
+  final VoidCallback? onTap;
+  final bool esCompacta;
+
+  const TarjetaEmisora({
+    super.key,
+    required this.emisora,
+    this.onTap,
+    this.esCompacta = false,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Card(
+      clipBehavior: Clip.antiAlias,
+      child: InkWell(
+        onTap: onTap,
+        child: esCompacta ? _buildCompacta(theme) : _buildCompleta(theme),
+      ),
+    );
+  }
+
+  Widget _buildCompleta(ThemeData theme) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        AspectRatio(
+          aspectRatio: 1,
+          child: _logo(theme, 60),
+        ),
+        Padding(
+          padding: const EdgeInsets.all(8),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(
+                emisora.nombre,
+                style: theme.textTheme.bodyMedium?.copyWith(fontWeight: FontWeight.bold),
+                maxLines: 2,
+                overflow: TextOverflow.ellipsis,
+              ),
+              if (emisora.pais != null)
+                Text(
+                  emisora.pais!,
+                  style: theme.textTheme.bodySmall?.copyWith(
+                    color: theme.colorScheme.onSurfaceVariant,
+                  ),
+                  maxLines: 1,
+                  overflow: TextOverflow.ellipsis,
+                ),
+            ],
+          ),
+        ),
+      ],
+    );
+  }
+
+  Widget _buildCompacta(ThemeData theme) {
+    return ListTile(
+      leading: SizedBox(width: 48, height: 48, child: _logo(theme, 24)),
+      title: Text(
+        emisora.nombre,
+        maxLines: 1,
+        overflow: TextOverflow.ellipsis,
+      ),
+      subtitle: Text(
+        [emisora.pais, emisora.idioma].where((s) => s != null).join(' · '),
+        maxLines: 1,
+        overflow: TextOverflow.ellipsis,
+      ),
+    );
+  }
+
+  Widget _logo(ThemeData theme, double iconSize) {
+    if (emisora.favicon != null && emisora.favicon!.isNotEmpty) {
+      return CachedNetworkImage(
+        imageUrl: emisora.favicon!,
+        fit: BoxFit.cover,
+        placeholder: (_, __) => _shimmer(theme),
+        errorWidget: (_, __, ___) => _iconoFallback(theme, iconSize),
+      );
+    }
+    return _iconoFallback(theme, iconSize);
+  }
+
+  Widget _shimmer(ThemeData theme) {
+    return Shimmer.fromColors(
+      baseColor: theme.colorScheme.surfaceContainerHighest,
+      highlightColor: theme.colorScheme.surface,
+      child: Container(color: theme.colorScheme.surfaceContainerHighest),
+    );
+  }
+
+  Widget _iconoFallback(ThemeData theme, double size) {
+    return Container(
+      color: theme.colorScheme.primaryContainer,
+      child: Icon(Icons.radio, size: size, color: theme.colorScheme.onPrimaryContainer),
+    );
+  }
+}
+
+/// Placeholder shimmer para listas en carga.
+class TarjetaEmisoraShimmer extends StatelessWidget {
+  const TarjetaEmisoraShimmer({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Shimmer.fromColors(
+      baseColor: theme.colorScheme.surfaceContainerHighest,
+      highlightColor: theme.colorScheme.surface,
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          AspectRatio(
+            aspectRatio: 1,
+            child: Container(color: theme.colorScheme.surfaceContainerHighest),
+          ),
+          const SizedBox(height: 8),
+          Container(height: 14, color: theme.colorScheme.surfaceContainerHighest),
+          const SizedBox(height: 4),
+          Container(height: 12, width: 60, color: theme.colorScheme.surfaceContainerHighest),
+        ],
+      ),
+    );
+  }
+}