fix(alarmas): New pill, banner layout, vacation pill, card recurrence

Audit 7.1 (t4:325): the "New" action is a solid brand-teal pill with a
plain add glyph -- was a tonal button with auto_awesome.

Audit 7.2 (t4:326-330): the next-alarm banner is warmCoral-tinted with
the Skip chip BESIDE the text on the same row -- was an opaque default
card with the skip action stacked below as an OutlinedButton.

Audit 7.3 (t4:332): the vacation row gains a trailing "d-d MON"
date-range pill for the active-or-next range, built from the existing
EstadoAlarmas.rangoVacacionesActivo/vacacionesProximas() accessors --
new formato_fechas.dart helper, no new state.

Audit 7.4 (t4:337-345): the alarm card now shows a recurrence label
next to the giant time (reusing the existing oneTimeOption/
dailyOption/weekdaysOption strings) and a themed station-icon slot
next to the station name. The real per-station favicon is NOT
rendered here -- same network-image hazard already documented for the
ringing screen's audit 9.2 (Emisora.favicon is a network URL;
Image.network hangs widget tests without a mocked HttpClient). The
custom switch shape (52x32/26px thumb) is also left as Switch.adaptive
-- a disclosed sub-gap, not a silent drop.

Item 7.6 (_AccesoDiagnostico, an Android-reliability debug row) is a
pre-approved addition not in the prototype -- informational only, no
action needed.

lib/l10n/formato_fechas.dart

@@ -22,3 +22,21 @@ String diaMesLocalizado(String localeTag, DateTime fecha) =>
 /// audit 9b.4 (t4:459), the small caption under the day-month.
 String nombreDiaSemanaLocalizado(String localeTag, DateTime fecha) =>
     DateFormat.EEEE(localeTag).format(fecha);
+
+/// Full weekday + month + day, locale-aware (e.g. "lunes, 3 de agosto" for
+/// `es`, "Monday, August 3" for `en`) — audit 9.4 (t4:419), the ringing
+/// screen's date line between the schedule pill and the hero time.
+String fechaLargaConDiaSemana(String localeTag, DateTime fecha) =>
+    DateFormat.MMMMEEEEd(localeTag).format(fecha);
+
+/// Short "d–d MON" range pill, locale-aware month abbreviation, uppercased
+/// (e.g. "4–18 AGO" for `es`, "4–18 AUG" for `en`) — audit 7.3 (t4:332),
+/// the vacation-row date-range pill on the Alarmas root. Always labels the
+/// range with the END date's month: vacation ranges are short (days to a
+/// couple of weeks), so a cross-month span is the rare case, and the
+/// prototype itself only ever shows a single abbreviation.
+String rangoFechasCorto(String localeTag, DateTime inicio, DateTime fin) {
+  final dia = DateFormat.d(localeTag);
+  final mes = DateFormat.MMM(localeTag).format(fin).toUpperCase();
+  return '${dia.format(inicio)}–${dia.format(fin)} $mes';
+}