feat(alarmas): simplify alarm cards and add vacation summary row

Restyle the Alarmas root per the functional redesign: alarm cards drop
the always-visible edit/skip/delete button row for a minimal giant
time + station + switch layout. Tap opens the editor, swipe deletes
(with an AlertDialog confirmation), and the hero banner gains an
inline "Saltar" pill for the featured (soonest-firing) alarm's skip
action. No capability from the old button row is lost, only the
trigger location moved; estado_alarmas.dart and its scheduling/
snooze/dismiss-guard tests are untouched.

The vacation inline panel becomes a tappable summary row (range count
+ next-range countdown, computed over the existing estado.vacaciones)
that pushes a Vacaciones manager screen. That destination is a
placeholder for now (_PantallaVacacionesTemporal, holding the old
panel's body verbatim so add/delete-range capability is preserved) --
WU9 replaces it with the real PantallaVacaciones per design ADR-6.

New ARB keys (en/es only; other 11 locales are WU18's job):
alarmHeroSkipAction, alarmDeleteConfirmTitle/Message,
vacationRangesCount, vacationSummary{Active,Upcoming}Countdown.

lib/l10n/app_en.arb

@@ -422,6 +422,9 @@
   "editAction": "Edit",
   "skipNextAction": "Skip next",
   "deleteTooltip": "Delete",
+  "alarmHeroSkipAction": "Skip",
+  "alarmDeleteConfirmTitle": "Delete alarm?",
+  "alarmDeleteConfirmMessage": "This can't be undone.",
   "alarmSkippedNoNextSnackbar": "Alarm skipped. There is no next occurrence left.",
   "alarmSkippedReturnsSnackbar": "Alarm skipped. It will return on {date}.",
   "@alarmSkippedReturnsSnackbar": {
@@ -508,6 +511,30 @@
   "vacationRangesHint": "If an alarm is set to \"Paused during vacations\", it automatically skips these ranges.",
   "noVacationRangesLoaded": "No ranges loaded.",
   "deleteRangeTooltip": "Delete range",
+  "vacationRangesCount": "{count} ranges",
+  "@vacationRangesCount": {
+    "placeholders": {
+      "count": {
+        "type": "int"
+      }
+    }
+  },
+  "vacationSummaryActiveCountdown": "Active now · {days} days left",
+  "@vacationSummaryActiveCountdown": {
+    "placeholders": {
+      "days": {
+        "type": "int"
+      }
+    }
+  },
+  "vacationSummaryUpcomingCountdown": "Next range in {days} days",
+  "@vacationSummaryUpcomingCountdown": {
+    "placeholders": {
+      "days": {
+        "type": "int"
+      }
+    }
+  },
   "vacationsDefaultName": "Vacation",
   "newVacationRangeTitle": "New vacation range",
   "startField": "Start",