feat(v0.3.0): ecualizador + favoritos en tarjeta + emisoras custom + export/import + fix MainActivity

- MainActivity: extiende AudioServiceActivity (fix pantalla en blanco)
- ServicioAudio: AndroidEqualizer en AudioPipeline, aplicarPreset(), setBanda()
- PresetEcualizador: modelo independiente (Flat/Rock/Pop/BassBoost/Jazz/Voz)
- EcualizadorWidget: 5 sliders verticales + PresetsEcualizadorWidget
- TarjetaEmisora: botón favorito visible en grid y lista (toggle con SnackBar)
- EstadoRadio: emisoras custom (CRUD), export/import JSON v1, presets por emisora
- PantallaAjustes: ecualizador interactivo, form añadir emisora, backup export/import
- pubspec: +file_picker ^8.1.7, +uuid ^4.5.1

lib/pantallas/pantalla_ajustes.dart

@@ -1,42 +1,387 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:file_picker/file_picker.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:share_plus/share_plus.dart' show Share, XFile;
+import 'package:path_provider/path_provider.dart';
+import 'package:uuid/uuid.dart';
 import '../estado/estado_radio.dart';
+import '../modelos/emisora.dart';
+import '../modelos/preset_ecualizador.dart';
+import '../widgets/ecualizador_widget.dart';
 
-/// Pantalla de ajustes — por ahora muestra info de la app.
-/// En Fase 3 se añadirá Export/Import config y gestión PRO.
 class PantallaAjustes extends StatelessWidget {
   const PantallaAjustes({super.key});
 
   @override
   Widget build(BuildContext context) {
-    final theme = Theme.of(context);
-    final estado = context.read<EstadoRadio>();
-
     return Scaffold(
       appBar: AppBar(title: const Text('Ajustes')),
       body: ListView(
+        children: const [
+          _SeccionEcualizador(),
+          Divider(),
+          _SeccionEmisoras(),
+          Divider(),
+          _SeccionBackup(),
+          Divider(),
+          _SeccionInfo(),
+        ],
+      ),
+    );
+  }
+}
+
+// ── Sección Ecualizador ───────────────────────────────────────────────────────
+
+class _SeccionEcualizador extends StatelessWidget {
+  const _SeccionEcualizador();
+
+  @override
+  Widget build(BuildContext context) {
+    return Consumer<EstadoRadio>(
+      builder: (ctx, estado, _) {
+        final disponible = estado.ecualizadorDisponible;
+        return Padding(
+          padding: const EdgeInsets.all(16),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: [
+              Row(
+                children: [
+                  const Icon(Icons.equalizer),
+                  const SizedBox(width: 12),
+                  Text('Ecualizador', style: Theme.of(ctx).textTheme.titleMedium),
+                  const Spacer(),
+                  if (!disponible)
+                    Chip(
+                      label: const Text('Reproduce una emisora para activar'),
+                      visualDensity: VisualDensity.compact,
+                    ),
+                ],
+              ),
+              if (disponible) ...[
+                const SizedBox(height: 8),
+                PresetsEcualizadorWidget(
+                  presetActual: estado.presetEcualizador,
+                  onSeleccionar: (p) => estado.cambiarPresetEcualizador(p),
+                ),
+                const SizedBox(height: 12),
+                EcualizadorWidget(
+                  preset: estado.presetEcualizador,
+                  onCambio: (p) {
+                    for (int i = 0; i < p.bandas.length; i++) {
+                      estado.cambiarBandaEcualizador(i, p.bandas[i]);
+                    }
+                  },
+                ),
+              ],
+            ],
+          ),
+        );
+      },
+    );
+  }
+}
+
+// ── Sección Emisoras personalizadas ──────────────────────────────────────────
+
+class _SeccionEmisoras extends StatelessWidget {
+  const _SeccionEmisoras();
+
+  @override
+  Widget build(BuildContext context) {
+    final estado = context.watch<EstadoRadio>();
+    final custom = estado.emisorasCustom;
+
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Padding(
+          padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
+          child: Row(
+            children: [
+              const Icon(Icons.add_circle_outline),
+              const SizedBox(width: 12),
+              Text('Emisoras personalizadas',
+                  style: Theme.of(context).textTheme.titleMedium),
+              const Spacer(),
+              TextButton.icon(
+                icon: const Icon(Icons.add),
+                label: const Text('Añadir'),
+                onPressed: () => _mostrarFormularioAnadir(context),
+              ),
+            ],
+          ),
+        ),
+        if (custom.isEmpty)
+          const Padding(
+            padding: EdgeInsets.fromLTRB(16, 4, 16, 12),
+            child: Text('No hay emisoras personalizadas.',
+                style: TextStyle(color: Colors.grey)),
+          )
+        else
+          for (final emisora in custom)
+            ListTile(
+              leading: const Icon(Icons.radio),
+              title: Text(emisora.nombre),
+              subtitle: Text(emisora.url, maxLines: 1, overflow: TextOverflow.ellipsis),
+              trailing: Row(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  IconButton(
+                    icon: const Icon(Icons.play_arrow),
+                    tooltip: 'Reproducir',
+                    onPressed: () => context.read<EstadoRadio>().reproducir(emisora),
+                  ),
+                  IconButton(
+                    icon: const Icon(Icons.delete_outline),
+                    tooltip: 'Eliminar',
+                    onPressed: () => context.read<EstadoRadio>().eliminarEmitoraCustom(emisora.uuid),
+                  ),
+                ],
+              ),
+            ),
+      ],
+    );
+  }
+
+  Future<void> _mostrarFormularioAnadir(BuildContext context) async {
+    await showModalBottomSheet(
+      context: context,
+      isScrollControlled: true,
+      builder: (ctx) => const _FormularioEmisora(),
+    );
+  }
+}
+
+class _FormularioEmisora extends StatefulWidget {
+  const _FormularioEmisora();
+
+  @override
+  State<_FormularioEmisora> createState() => _FormularioEmisoraState();
+}
+
+class _FormularioEmisoraState extends State<_FormularioEmisora> {
+  final _formKey = GlobalKey<FormState>();
+  final _nombreCtrl = TextEditingController();
+  final _urlCtrl = TextEditingController();
+  final _paisCtrl = TextEditingController();
+  bool _guardando = false;
+
+  @override
+  void dispose() {
+    _nombreCtrl.dispose();
+    _urlCtrl.dispose();
+    _paisCtrl.dispose();
+    super.dispose();
+  }
+
+  Future<void> _guardar() async {
+    if (!_formKey.currentState!.validate()) return;
+    setState(() => _guardando = true);
+
+    final emisora = Emisora(
+      uuid: const Uuid().v4(),
+      nombre: _nombreCtrl.text.trim(),
+      url: _urlCtrl.text.trim(),
+      pais: _paisCtrl.text.trim().isEmpty ? null : _paisCtrl.text.trim(),
+    );
+
+    await context.read<EstadoRadio>().agregarEmitoraCustom(emisora);
+    if (mounted) Navigator.pop(context);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final bottom = MediaQuery.of(context).viewInsets.bottom;
+    return Padding(
+      padding: EdgeInsets.fromLTRB(16, 16, 16, 16 + bottom),
+      child: Form(
+        key: _formKey,
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            Text('Añadir emisora', style: Theme.of(context).textTheme.titleLarge),
+            const SizedBox(height: 16),
+            TextFormField(
+              controller: _nombreCtrl,
+              decoration: const InputDecoration(labelText: 'Nombre *', border: OutlineInputBorder()),
+              validator: (v) => v == null || v.trim().isEmpty ? 'Campo obligatorio' : null,
+            ),
+            const SizedBox(height: 12),
+            TextFormField(
+              controller: _urlCtrl,
+              decoration: const InputDecoration(
+                labelText: 'URL del stream *',
+                hintText: 'http://stream.ejemplo.com:8000/radio',
+                border: OutlineInputBorder(),
+              ),
+              keyboardType: TextInputType.url,
+              validator: (v) {
+                if (v == null || v.trim().isEmpty) return 'Campo obligatorio';
+                final uri = Uri.tryParse(v.trim());
+                if (uri == null || !uri.hasScheme) return 'URL no válida';
+                return null;
+              },
+            ),
+            const SizedBox(height: 12),
+            TextFormField(
+              controller: _paisCtrl,
+              decoration: const InputDecoration(
+                labelText: 'País (opcional)',
+                border: OutlineInputBorder(),
+              ),
+            ),
+            const SizedBox(height: 20),
+            FilledButton(
+              onPressed: _guardando ? null : _guardar,
+              child: _guardando
+                  ? const SizedBox(height: 20, width: 20, child: CircularProgressIndicator(strokeWidth: 2))
+                  : const Text('Guardar emisora'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+// ── Sección Backup ────────────────────────────────────────────────────────────
+
+class _SeccionBackup extends StatelessWidget {
+  const _SeccionBackup();
+
+  Future<void> _exportar(BuildContext context) async {
+    try {
+      final estado = context.read<EstadoRadio>();
+      final config = await estado.exportarConfig();
+      final json = const JsonEncoder.withIndent('  ').convert(config);
+
+      final dir = await getTemporaryDirectory();
+      final file = File('${dir.path}/pluriwave-backup.json');
+      await file.writeAsString(json);
+
+      await Share.shareXFiles(
+        [XFile(file.path)],
+        subject: 'PluriWave — copia de seguridad',
+        text: 'Configuración de PluriWave exportada el ${DateTime.now().toLocal()}',
+      );
+    } catch (e) {
+      if (context.mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('Error al exportar: $e')),
+        );
+      }
+    }
+  }
+
+  Future<void> _importar(BuildContext context) async {
+    try {
+      final result = await FilePicker.platform.pickFiles(
+        type: FileType.custom,
+        allowedExtensions: ['json'],
+      );
+      if (result == null || result.files.single.path == null) return;
+
+      final file = File(result.files.single.path!);
+      final json = jsonDecode(await file.readAsString()) as Map<String, dynamic>;
+
+      if (context.mounted) {
+        final confirmar = await showDialog<bool>(
+          context: context,
+          builder: (ctx) => AlertDialog(
+            title: const Text('Importar configuración'),
+            content: const Text(
+                'Esto añadirá los favoritos, emisoras y presets del fichero. '
+                '¿Continuar?'),
+            actions: [
+              TextButton(
+                  onPressed: () => Navigator.pop(ctx, false),
+                  child: const Text('Cancelar')),
+              FilledButton(
+                  onPressed: () => Navigator.pop(ctx, true),
+                  child: const Text('Importar')),
+            ],
+          ),
+        );
+        if (confirmar != true) return;
+        if (context.mounted) {
+          await context.read<EstadoRadio>().importarConfig(json);
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(content: Text('Configuración importada correctamente')),
+          );
+        }
+      }
+    } catch (e) {
+      if (context.mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('Error al importar: $e')),
+        );
+      }
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Padding(
+          padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
+          child: Row(
+            children: [
+              const Icon(Icons.backup_outlined),
+              const SizedBox(width: 12),
+              Text('Copia de seguridad',
+                  style: Theme.of(context).textTheme.titleMedium),
+            ],
+          ),
+        ),
+        ListTile(
+          leading: const Icon(Icons.upload_outlined),
+          title: const Text('Exportar configuración'),
+          subtitle: const Text('Favoritos, emisoras custom y presets de EQ'),
+          onTap: () => _exportar(context),
+        ),
+        ListTile(
+          leading: const Icon(Icons.download_outlined),
+          title: const Text('Importar configuración'),
+          subtitle: const Text('Restaurar desde un fichero de copia de seguridad'),
+          onTap: () => _importar(context),
+        ),
+      ],
+    );
+  }
+}
+
+// ── Sección Info ──────────────────────────────────────────────────────────────
+
+class _SeccionInfo extends StatelessWidget {
+  const _SeccionInfo();
+
+  @override
+  Widget build(BuildContext context) {
+    return Consumer<EstadoRadio>(
+      builder: (ctx, estado, _) => Column(
         children: [
-          // Info app
           ListTile(
             leading: const Icon(Icons.info_outline),
             title: const Text('PluriWave'),
             subtitle: const Text('v0.3.0 — Radio mundial'),
           ),
-          const Divider(),
-          // Favoritos
           FutureBuilder<int>(
             future: estado.favoritos.obtenerTodos().then((l) => l.length),
             builder: (ctx, snap) => ListTile(
               leading: const Icon(Icons.favorite_outline),
               title: const Text('Favoritos guardados'),
-              trailing: Text(
-                snap.data?.toString() ?? '—',
-                style: theme.textTheme.bodyLarge,
-              ),
+              trailing: Text(snap.data?.toString() ?? '—',
+                  style: Theme.of(ctx).textTheme.bodyLarge),
             ),
           ),
-          const Divider(),
-          // Filtro emisoras
           ListTile(
             leading: const Icon(Icons.verified_outlined),
             title: const Text('Filtro de emisoras'),
@@ -44,39 +389,11 @@ class PantallaAjustes extends StatelessWidget {
             trailing: const Icon(Icons.check_circle, color: Colors.green),
           ),
           ListTile(
-            leading: const Icon(Icons.music_off_outlined),
+            leading: const Icon(Icons.music_note_outlined),
             title: const Text('Audio en background'),
-            subtitle: const Text('Activo — continúa al apagar pantalla'),
+            subtitle: const Text('Continúa al apagar la pantalla'),
             trailing: const Icon(Icons.check_circle, color: Colors.green),
           ),
-          const Divider(),
-          // Próximamente
-          const Padding(
-            padding: EdgeInsets.fromLTRB(16, 12, 16, 4),
-            child: Text('PRÓXIMAMENTE', style: TextStyle(fontSize: 12, letterSpacing: 1.2)),
-          ),
-          ListTile(
-            leading: const Icon(Icons.upload_outlined),
-            title: const Text('Exportar configuración'),
-            subtitle: const Text('Favoritos, radios custom, presets EQ'),
-            enabled: false,
-          ),
-          ListTile(
-            leading: const Icon(Icons.download_outlined),
-            title: const Text('Importar configuración'),
-            enabled: false,
-          ),
-          ListTile(
-            leading: const Icon(Icons.add_circle_outline),
-            title: const Text('Añadir radio personalizada'),
-            enabled: false,
-          ),
-          ListTile(
-            leading: const Icon(Icons.equalizer_outlined),
-            title: const Text('Ecualizador'),
-            subtitle: const Text('5 bandas, presets por emisora'),
-            enabled: false,
-          ),
         ],
       ),
     );