fix(vacaciones): replace the progress bar with the prototype's date pair

Item 21 / audit 9b.4-9b.5 (t4:451-462, 469-479): the active vacation
range showed a LinearProgressIndicator the prototype never draws.
Replace it with the screen's real signature element -- a start/end
date pair (day+month, weekday, connector rule) -- reused with a flat
connector for the "programados"/"pasados" rows, replacing their plain
ListTiles with proper cards.

test/pantallas/pantalla_vacaciones_test.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:pluriwave/estado/estado_alarmas.dart';
+import 'package:pluriwave/l10n/formato_fechas.dart';
 import 'package:pluriwave/l10n/gen/app_localizations.dart';
 import 'package:pluriwave/modelos/alarma_musical.dart';
 import 'package:pluriwave/pantallas/pantalla_vacaciones.dart';
@@ -221,4 +222,125 @@ void main() {
 
     expect(find.text(l10n.newVacationRangeTitle), findsOneWidget);
   });
+
+  // Item 21 / audit 9b.4-9b.5 (t4:451-462, 469-479): the screen's signature
+  // element is a start/end date pair, never a determinate progress bar.
+  testWidgets(
+    'el rango activo muestra el par de fechas, no una barra de progreso',
+    (tester) async {
+      final inicio = _hoyDia.subtract(const Duration(days: 3));
+      final fin = _hoyDia.add(const Duration(days: 5));
+      final estado = await _crearEstado(
+        vacaciones: [
+          RangoVacaciones(
+            id: 'v1',
+            nombre: 'Julio activo',
+            inicio: inicio,
+            fin: fin,
+          ),
+        ],
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(_buildScreen(estado));
+      await _pumpEstable(tester);
+
+      expect(
+        find.byType(LinearProgressIndicator),
+        findsNothing,
+        reason:
+            't4:451-462 replaces the progress bar with a start/end date '
+            'pair — the screen\'s signature element',
+      );
+
+      expect(find.text(diaMesLocalizado('es', inicio)), findsOneWidget);
+      expect(find.text(diaMesLocalizado('es', fin)), findsOneWidget);
+      expect(
+        find.text(nombreDiaSemanaLocalizado('es', inicio)),
+        findsOneWidget,
+      );
+      expect(find.text(nombreDiaSemanaLocalizado('es', fin)), findsOneWidget);
+
+      final fechaTexto = tester.widget<Text>(
+        find.text(diaMesLocalizado('es', inicio)),
+      );
+      expect(
+        fechaTexto.style?.fontSize,
+        26,
+        reason: 't4:459 the date digits are 26px/w800/ls-1',
+      );
+      expect(fechaTexto.style?.fontWeight, FontWeight.w800);
+
+      final diaSemanaTexto = tester.widget<Text>(
+        find.text(nombreDiaSemanaLocalizado('es', inicio)),
+      );
+      expect(
+        diaSemanaTexto.style?.fontSize,
+        11,
+        reason: 't4:459 the weekday caption is 11px/w700/50%',
+      );
+      expect(diaSemanaTexto.style?.fontWeight, FontWeight.w700);
+
+      final regla = tester.widget<DecoratedBox>(
+        find.byKey(const ValueKey('vacaciones-regla-activo')),
+      );
+      final decoration = regla.decoration as BoxDecoration;
+      expect(
+        decoration.gradient,
+        isNotNull,
+        reason:
+            't4:460 the active range connector is a brand-teal gradient, '
+            'not the flat rgba(255,255,255,.14) used by scheduled rows',
+      );
+    },
+  );
+
+  testWidgets(
+    'un rango programado usa el mismo par de fechas, con una regla plana y '
+    'una fila de etiqueta con el nombre del rango',
+    (tester) async {
+      final inicio = _hoyDia.add(const Duration(days: 20));
+      final fin = _hoyDia.add(const Duration(days: 25));
+      final estado = await _crearEstado(
+        vacaciones: [
+          RangoVacaciones(id: 'f2', nombre: 'Verano', inicio: inicio, fin: fin),
+        ],
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(_buildScreen(estado));
+      await _pumpEstable(tester);
+
+      expect(
+        find.descendant(
+          of: find.byType(PantallaVacaciones),
+          matching: find.byType(ListTile),
+        ),
+        findsNothing,
+        reason: '9b.5 (t4:469-479) replaces the ListTile row with a card',
+      );
+      expect(find.text(diaMesLocalizado('es', inicio)), findsOneWidget);
+      expect(find.text(diaMesLocalizado('es', fin)), findsOneWidget);
+      expect(
+        find.text('Verano'),
+        findsOneWidget,
+        reason:
+            't4:478 the label row shows the range name next to a '
+            '"label" icon',
+      );
+
+      final regla = tester.widget<DecoratedBox>(
+        find.byKey(const ValueKey('vacaciones-regla-f2')),
+      );
+      final decoration = regla.decoration as BoxDecoration;
+      expect(decoration.gradient, isNull);
+      expect(
+        decoration.color,
+        Colors.white.withValues(alpha: 0.14),
+        reason:
+            't4:474 scheduled/past rows use a flat rgba(255,255,255,.14) '
+            'connector, not the active gradient',
+      );
+    },
+  );
 }