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/app_en.arb

@@ -233,6 +233,7 @@
       }
     }
   },
+  "recordingsLibraryStorageFolderCaption": "Music/PluriWave · purges oldest at limit",
   "recordingsLibraryEmptyTitle": "No recordings yet",
   "recordingsLibraryEmptySubtitle": "Recordings you save will appear here.",
   "recordingActionRename": "Rename",
@@ -315,13 +316,17 @@
   "searchCountryFilterLabel": "Country",
   "searchLanguageFilterLabel": "Language",
   "searchMinQualityFilterLabel": "Minimum quality",
+  "searchLoadingStationsLabel": "SEARCHING FOR STATIONS…",
   "searchEmptyTitle": "Search for a station",
   "searchNoResultsTitle": "No results",
+  "searchNoResultsForQueryTitle": "No results for \"{query}\"",
+  "@searchNoResultsForQueryTitle": {"placeholders": {"query": {}}},
   "searchEmptySubtitle": "Use the top bar or chips to discover stations from around the world.",
   "searchNoResultsSubtitle": "Try removing filters or typing another name to find an active station.",
   "searchResultsCount": "{count, plural, =1{1 result} other{{count} results}}",
   "searchClearFiltersAction": "{count, plural, =1{Clear filter} other{Clear {count} filters}}",
   "countriesScreenTitle": "Countries",
+  "countriesSearchHint": "Country or code...",
   "countriesYourLanguagesTitle": "Your languages",
   "countriesAllTitle": "All countries",
   "radioCountriesError": "We couldn't load the countries.",
@@ -509,6 +514,7 @@
       }
     }
   },
+  "alarmSnoozeUsualLabel": "usual",
   "saveFavoritesAlarmHint": "Save stations in Favorites to use them as a music alarm.",
   "useCurrentStationAction": "Use current station",
   "playDuringVacations": "Play during vacations",
@@ -698,6 +704,7 @@
       "days": {}
     }
   },
+  "alarmRepeatSectionLabel": "REPEAT",
   "androidReliabilityTitle": "Review Android reliability",
   "closeAction": "Close",
   "customOption": "Custom",