fix(eq): split the equalizer body into 4 cards, add Restablecer a plano

Audit 11.10/11.8 (t4 lines 570-602): the prototype draws the explainer
banner, the band sliders, "Salida activa + Guardar como preset +
Restablecer a plano" and "Emisoras con ajuste propio" as 4 separate
cards. The build nested everything in one outer PluriGlassSurface, so
it read as a single merged block, and had no reset-to-flat action at
all.

Removes the outer wrapper from _CuerpoEcualizador. EcualizadorWidget
already draws its own card (design ADR-5, unchanged); the explainer
banner already has its own tinted background (unchanged); "Emisoras
con ajuste propio" now wraps itself in its own PluriGlassSurface; a
new _TarjetaSalidaYAcciones groups Salida activa with two tappable
rows — "Guardar como preset" (relocated from a floating end-aligned
button) and the new "Restablecer a plano", which applies
PresetEcualizador.flat via the existing EstadoEcualizador.cambiarPreset
— the same call the "Plano" preset chip already makes, not a new
capability.

The 5-slider band count, servicio_ecualizador.dart and
preset_ecualizador.dart are untouched.

lib/l10n/app_ar.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "المخرج النشط",
   "equalizerBaseExplainer": "هذا هو المعادل الأساسي: يُطبَّق على كل محطة لا تملك إعدادًا خاصًا بها. يُحدَّد معادل محطة معينة من شاشة تشغيلها الخاصة، وله الأولوية على هذا المعادل.",
   "equalizerSaveAsPresetAction": "حفظ كإعداد مسبق",
+  "equalizerResetToFlatAction": "إعادة الضبط إلى مسطح",
   "equalizerSavePresetConfirm": "حفظ",
   "equalizerSavePresetDialogTitle": "حفظ كإعداد مسبق",
   "equalizerSavePresetEmptyNameError": "أدخل اسمًا للإعداد المسبق.",

lib/l10n/app_bn.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "সক্রিয় আউটপুট",
   "equalizerBaseExplainer": "এটি বেস ইকুয়ালাইজার: এটি নিজস্ব সেটিং নেই এমন সব স্টেশনে প্রযোজ্য। কোনো নির্দিষ্ট স্টেশনের নিজস্ব EQ তার প্লেব্যাক স্ক্রিন থেকে ঠিক করা হয় এবং এটির চেয়ে অগ্রাধিকার পায়।",
   "equalizerSaveAsPresetAction": "প্রিসেট হিসেবে সংরক্ষণ করুন",
+  "equalizerResetToFlatAction": "সমতলে পুনরায় সেট করুন",
   "equalizerSavePresetConfirm": "সংরক্ষণ করুন",
   "equalizerSavePresetDialogTitle": "প্রিসেট হিসেবে সংরক্ষণ করুন",
   "equalizerSavePresetEmptyNameError": "প্রিসেটের জন্য একটি নাম লিখুন।",

lib/l10n/app_de.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Aktiver Ausgang",
   "equalizerBaseExplainer": "Dies ist der Basis-Equalizer: Er gilt für alle Sender ohne eigene Einstellung. Der eigene EQ eines Senders wird auf dessen eigenem Wiedergabebildschirm festgelegt und hat Vorrang vor diesem hier.",
   "equalizerSaveAsPresetAction": "Als Preset speichern",
+  "equalizerResetToFlatAction": "Auf neutral zurücksetzen",
   "equalizerSavePresetConfirm": "Speichern",
   "equalizerSavePresetDialogTitle": "Als Preset speichern",
   "equalizerSavePresetEmptyNameError": "Gib einen Namen für das Preset ein.",

lib/l10n/app_en.arb

@@ -102,6 +102,7 @@
   "equalizerStationsWithOwnEqSubtitle": "Ignore this base equalizer",
   "equalizerStationsWithOwnEqEmpty": "No stations have their own EQ yet.",
   "equalizerSaveAsPresetAction": "Save as preset",
+  "equalizerResetToFlatAction": "Reset to flat",
   "equalizerSavePresetDialogTitle": "Save as preset",
   "equalizerSavePresetNameLabel": "Preset name",
   "equalizerSavePresetEmptyNameError": "Enter a name for the preset.",

lib/l10n/app_es.arb

@@ -102,6 +102,7 @@
   "equalizerStationsWithOwnEqSubtitle": "Ignoran este ecualizador base",
   "equalizerStationsWithOwnEqEmpty": "Ninguna emisora tiene ajuste propio todavía.",
   "equalizerSaveAsPresetAction": "Guardar como preset",
+  "equalizerResetToFlatAction": "Restablecer a plano",
   "equalizerSavePresetDialogTitle": "Guardar como preset",
   "equalizerSavePresetNameLabel": "Nombre del preset",
   "equalizerSavePresetEmptyNameError": "Ingresá un nombre para el preset.",

lib/l10n/app_fr.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Sortie active",
   "equalizerBaseExplainer": "Voici l'égaliseur de base : il s'applique à toutes les stations sans réglage propre. L'EQ propre à une station est défini depuis son propre écran de lecture et prime sur celui-ci.",
   "equalizerSaveAsPresetAction": "Enregistrer comme Preset",
+  "equalizerResetToFlatAction": "Réinitialiser à plat",
   "equalizerSavePresetConfirm": "Enregistrer",
   "equalizerSavePresetDialogTitle": "Enregistrer comme Preset",
   "equalizerSavePresetEmptyNameError": "Saisissez un nom pour le Preset.",

lib/l10n/app_hi.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "सक्रिय आउटपुट",
   "equalizerBaseExplainer": "यह बेस इक्वलाइज़र है: यह उन सभी स्टेशन पर लागू होता है जिनकी अपनी सेटिंग नहीं है। किसी खास स्टेशन का अपना EQ उसकी प्लेबैक स्क्रीन से तय होता है और इस पर प्राथमिकता रखता है।",
   "equalizerSaveAsPresetAction": "प्रीसेट के रूप में सहेजें",
+  "equalizerResetToFlatAction": "समतल पर रीसेट करें",
   "equalizerSavePresetConfirm": "सहेजें",
   "equalizerSavePresetDialogTitle": "प्रीसेट के रूप में सहेजें",
   "equalizerSavePresetEmptyNameError": "प्रीसेट के लिए एक नाम डालें।",

lib/l10n/app_id.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Output aktif",
   "equalizerBaseExplainer": "Ini adalah equalizer dasar: berlaku untuk semua stasiun yang belum punya pengaturan sendiri. EQ khusus suatu stasiun diatur dari layar pemutarannya sendiri dan mengesampingkan yang ini.",
   "equalizerSaveAsPresetAction": "Simpan sebagai Preset",
+  "equalizerResetToFlatAction": "Setel ulang ke datar",
   "equalizerSavePresetConfirm": "Simpan",
   "equalizerSavePresetDialogTitle": "Simpan sebagai Preset",
   "equalizerSavePresetEmptyNameError": "Masukkan nama untuk Preset.",

lib/l10n/app_it.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Uscita attiva",
   "equalizerBaseExplainer": "Questo è l'equalizzatore di base: si applica a tutte le emittenti senza un'impostazione propria. L'EQ di un'emittente specifica si imposta dalla sua schermata di riproduzione e ha la precedenza su questo.",
   "equalizerSaveAsPresetAction": "Salva come Preset",
+  "equalizerResetToFlatAction": "Ripristina piatto",
   "equalizerSavePresetConfirm": "Salva",
   "equalizerSavePresetDialogTitle": "Salva come Preset",
   "equalizerSavePresetEmptyNameError": "Inserisci un nome per il Preset.",

lib/l10n/app_ja.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "アクティブな出力",
   "equalizerBaseExplainer": "これはベースイコライザーです。専用設定を持たないすべての局に適用されます。特定の局専用のEQはその局の再生画面から設定でき、こちらより優先されます。",
   "equalizerSaveAsPresetAction": "プリセットとして保存",
+  "equalizerResetToFlatAction": "フラットにリセット",
   "equalizerSavePresetConfirm": "保存",
   "equalizerSavePresetDialogTitle": "プリセットとして保存",
   "equalizerSavePresetEmptyNameError": "プリセットの名前を入力してください。",

lib/l10n/app_pt.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Saída ativa",
   "equalizerBaseExplainer": "Este é o equalizador base: aplica-se a todas as estações sem ajuste próprio. O EQ próprio de uma estação é definido na sua própria tela de reprodução e tem prioridade sobre este.",
   "equalizerSaveAsPresetAction": "Salvar como Preset",
+  "equalizerResetToFlatAction": "Repor para plano",
   "equalizerSavePresetConfirm": "Salvar",
   "equalizerSavePresetDialogTitle": "Salvar como Preset",
   "equalizerSavePresetEmptyNameError": "Digite um nome para o Preset.",

lib/l10n/app_ru.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "Активный выход",
   "equalizerBaseExplainer": "Это базовый эквалайзер: он применяется ко всем станциям без собственной настройки. Свой EQ конкретной станции задаётся на экране её воспроизведения и имеет приоритет над этим.",
   "equalizerSaveAsPresetAction": "Сохранить как пресет",
+  "equalizerResetToFlatAction": "Сбросить на плоский",
   "equalizerSavePresetConfirm": "Сохранить",
   "equalizerSavePresetDialogTitle": "Сохранить как пресет",
   "equalizerSavePresetEmptyNameError": "Введите название пресета.",

lib/l10n/app_zh.arb

@@ -711,6 +711,7 @@
   "equalizerActiveOutputLabel": "当前输出",
   "equalizerBaseExplainer": "这是基础均衡器：适用于所有没有专属设置的电台。某个电台的专属EQ可在其自己的播放界面中设置，并优先于此设置生效。",
   "equalizerSaveAsPresetAction": "保存为预设",
+  "equalizerResetToFlatAction": "重置为平坦",
   "equalizerSavePresetConfirm": "保存",
   "equalizerSavePresetDialogTitle": "保存为预设",
   "equalizerSavePresetEmptyNameError": "请输入预设名称。",

lib/l10n/gen/app_localizations.dart

@@ -538,6 +538,12 @@ abstract class AppLocalizations {
   /// **'Guardar como preset'**
   String get equalizerSaveAsPresetAction;
 
+  /// No description provided for @equalizerResetToFlatAction.
+  ///
+  /// In es, this message translates to:
+  /// **'Restablecer a plano'**
+  String get equalizerResetToFlatAction;
+
   /// No description provided for @equalizerSavePresetDialogTitle.
   ///
   /// In es, this message translates to:

lib/l10n/gen/app_localizations_ar.dart

@@ -246,6 +246,9 @@ class AppLocalizationsAr extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'حفظ كإعداد مسبق';
 
+  @override
+  String get equalizerResetToFlatAction => 'إعادة الضبط إلى مسطح';
+
   @override
   String get equalizerSavePresetDialogTitle => 'حفظ كإعداد مسبق';
 

lib/l10n/gen/app_localizations_bn.dart

@@ -250,6 +250,9 @@ class AppLocalizationsBn extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'প্রিসেট হিসেবে সংরক্ষণ করুন';
 
+  @override
+  String get equalizerResetToFlatAction => 'সমতলে পুনরায় সেট করুন';
+
   @override
   String get equalizerSavePresetDialogTitle => 'প্রিসেট হিসেবে সংরক্ষণ করুন';
 

lib/l10n/gen/app_localizations_de.dart

@@ -250,6 +250,9 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Als Preset speichern';
 
+  @override
+  String get equalizerResetToFlatAction => 'Auf neutral zurücksetzen';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Als Preset speichern';
 

lib/l10n/gen/app_localizations_en.dart

@@ -247,6 +247,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Save as preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Reset to flat';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Save as preset';
 

lib/l10n/gen/app_localizations_es.dart

@@ -249,6 +249,9 @@ class AppLocalizationsEs extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Guardar como preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Restablecer a plano';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Guardar como preset';
 

lib/l10n/gen/app_localizations_fr.dart

@@ -251,6 +251,9 @@ class AppLocalizationsFr extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Enregistrer comme Preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Réinitialiser à plat';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Enregistrer comme Preset';
 

lib/l10n/gen/app_localizations_hi.dart

@@ -249,6 +249,9 @@ class AppLocalizationsHi extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'प्रीसेट के रूप में सहेजें';
 
+  @override
+  String get equalizerResetToFlatAction => 'समतल पर रीसेट करें';
+
   @override
   String get equalizerSavePresetDialogTitle => 'प्रीसेट के रूप में सहेजें';
 

lib/l10n/gen/app_localizations_id.dart

@@ -249,6 +249,9 @@ class AppLocalizationsId extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Simpan sebagai Preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Setel ulang ke datar';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Simpan sebagai Preset';
 

lib/l10n/gen/app_localizations_it.dart

@@ -250,6 +250,9 @@ class AppLocalizationsIt extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Salva come Preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Ripristina piatto';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Salva come Preset';
 

lib/l10n/gen/app_localizations_ja.dart

@@ -239,6 +239,9 @@ class AppLocalizationsJa extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'プリセットとして保存';
 
+  @override
+  String get equalizerResetToFlatAction => 'フラットにリセット';
+
   @override
   String get equalizerSavePresetDialogTitle => 'プリセットとして保存';
 

lib/l10n/gen/app_localizations_pt.dart

@@ -248,6 +248,9 @@ class AppLocalizationsPt extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Salvar como Preset';
 
+  @override
+  String get equalizerResetToFlatAction => 'Repor para plano';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Salvar como Preset';
 

lib/l10n/gen/app_localizations_ru.dart

@@ -250,6 +250,9 @@ class AppLocalizationsRu extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => 'Сохранить как пресет';
 
+  @override
+  String get equalizerResetToFlatAction => 'Сбросить на плоский';
+
   @override
   String get equalizerSavePresetDialogTitle => 'Сохранить как пресет';
 

lib/l10n/gen/app_localizations_zh.dart

@@ -238,6 +238,9 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get equalizerSaveAsPresetAction => '保存为预设';
 
+  @override
+  String get equalizerResetToFlatAction => '重置为平坦';
+
   @override
   String get equalizerSavePresetDialogTitle => '保存为预设';