feat(alarms): native reliability fixes and end-to-end snooze

- Use mediaPlayback|systemExempted FGS type with FOREGROUND_SERVICE_SYSTEM_EXEMPTED so alarms fire on Android 14+ (FOREGROUND_SERVICE_ALARM does not exist in the SDK)
- Deduplicate fire notifications: the foreground service FSI notification is the single owner; receiver path removed
- Notification channel v2 with alarm sound URI and USAGE_ALARM attributes, one-time guarded migration from legacy channels
- Pass fallback station through the MethodChannel (NativeAlarmSpec schemaVersion 3) with a three-stage audio chain: primary -> fallback station -> bundled WAV
- Native fade-in volume ramp honoring fadeInSegundos when the app is killed
- Request battery-optimization exemption once, tracked with a persisted asked-once flag
- Fix snooze end-to-end: native ACTION_SNOOZE now reports back to Flutter (snoozed event + cold-start sync), snooze anchor unified to occurrence+minutes on both sides, periodic recalc no longer erases an active snooze
- Add snooze buttons (3/5/10/custom) to the ringing screen with shared audio teardown
- Redesign ringing screen on PluriWaveScaffold with reduced-motion-aware entry animation (new PluriAnimate helper)
- Alarm editor: live next-trigger preview, searchable station pickers (primary and fallback), configurable snooze duration, volume floor down to 0
- New alarm strings localized across all 13 locales
- New unit/widget tests for the snooze flow, alarm bridge payloads, ringing screen and editor (77 tests green)
- SDD artifacts for the app-quality-and-native-alarms change (explore, proposal, spec, design, tasks, apply progress)

lib/tema/pluri_animate.dart

@@ -0,0 +1,38 @@
+import 'package:flutter/widgets.dart';
+import 'package:flutter_animate/flutter_animate.dart';
+
+/// Reduced-motion-aware entry animations (S5-R3).
+///
+/// Every entry animation in the app should go through these helpers so the
+/// OS "disable animations" accessibility setting is honored from a single
+/// call site. When reduced motion is active the child is returned untouched
+/// (no [Animate] wrapper at all).
+extension PluriAnimate on Widget {
+  /// Fade-in entry animation.
+  Widget pluriFadeIn(
+    BuildContext context, {
+    Duration duration = const Duration(milliseconds: 350),
+    Duration delay = Duration.zero,
+    Curve curve = Curves.easeOutCubic,
+  }) {
+    if (_animacionesDeshabilitadas(context)) return this;
+    return animate(delay: delay).fadeIn(duration: duration, curve: curve);
+  }
+
+  /// Fade + subtle scale entry animation.
+  Widget pluriScaleIn(
+    BuildContext context, {
+    Duration duration = const Duration(milliseconds: 350),
+    Duration delay = Duration.zero,
+    Curve curve = Curves.easeOutCubic,
+    double begin = 0.96,
+  }) {
+    if (_animacionesDeshabilitadas(context)) return this;
+    return animate(delay: delay)
+        .fadeIn(duration: duration, curve: curve)
+        .scaleXY(begin: begin, end: 1, duration: duration, curve: curve);
+  }
+
+  bool _animacionesDeshabilitadas(BuildContext context) =>
+      MediaQuery.maybeDisableAnimationsOf(context) ?? false;
+}