fix(bienvenida,grabaciones): headline size, CTA radius, storage caption

Screen 14 / audit 14.3+14.7: welcome headline now 34px/ls-1.2 (was
headlineMedium's 28/ls-1.0), CTA restyled to a radius-18 rounded
rectangle instead of Material 3's default StadiumBorder (t4:696,715).

Screen 12 / audit 12.2+12.3: the recordings storage card now shows the
bold "X of Y used" headline ABOVE a 6px/radius-3 bar, followed by a
real folder-path + purge-policy caption below it -- was the bar first
with the "used" string as its only (small, generic) caption (t4:613).
New ARB key recordingsLibraryStorageFolderCaption, translated to all
13 locales.

Item 12.5 (folder/max-size settings living behind the header action
instead of inline on this screen) is a deliberate structural split
from WU15b; the audit itself scopes it out of this pass.

lib/l10n/gen/app_localizations_zh.dart

@@ -429,6 +429,10 @@ class AppLocalizationsZh extends AppLocalizations {
     return '已使用 $usedMb MB / 共 $totalMb MB';
   }
 
+  @override
+  String get recordingsLibraryStorageFolderCaption =>
+      'Music/PluriWave · 达到上限时会删除最旧的文件';
+
   @override
   String get recordingsLibraryEmptyTitle => '暂无录音';
 
@@ -592,12 +596,20 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get searchMinQualityFilterLabel => '最低质量';
 
+  @override
+  String get searchLoadingStationsLabel => '正在搜索电台…';
+
   @override
   String get searchEmptyTitle => '搜索电台';
 
   @override
   String get searchNoResultsTitle => '没有结果';
 
+  @override
+  String searchNoResultsForQueryTitle(Object query) {
+    return '未找到与\"$query\"相关的结果';
+  }
+
   @override
   String get searchEmptySubtitle => '使用顶部搜索栏或筛选标签，发现世界各地的电台信号。';
 
@@ -628,6 +640,9 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get countriesScreenTitle => '国家';
 
+  @override
+  String get countriesSearchHint => '国家或代码...';
+
   @override
   String get countriesYourLanguagesTitle => '你的语言';
 
@@ -981,6 +996,9 @@ class AppLocalizationsZh extends AppLocalizations {
     return '$minutes 分钟';
   }
 
+  @override
+  String get alarmSnoozeUsualLabel => '常用';
+
   @override
   String get saveFavoritesAlarmHint => '将电台保存到收藏，即可把它们用作音乐闹钟。';
 
@@ -1307,6 +1325,9 @@ class AppLocalizationsZh extends AppLocalizations {
     return '星期：$days';
   }
 
+  @override
+  String get alarmRepeatSectionLabel => '重复';
+
   @override
   String get androidReliabilityTitle => '检查 Android 可靠性';