feat(watch): clôture lot #91 - fréquence cardiaque live, notifications de séance et finitions montre

Consolide le lot applicatif watch companion validé :
- télémétrie fréquence cardiaque live remontée montre -> téléphone
  (collecteur watch, adapter Wear Data Layer, persistance Drift,
  propagation aux écrans historique/programme/profil/exécution)
- notifications de séance en arrière-plan côté téléphone (service
  foreground de statut + passerelle applicative)
- finitions montre : chrono d'étape, score d'étape, retrait du bouton
  "lancer une séance", thème, icônes et polices watch_app

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/application/session_notification_use_cases_test.dart

@@ -0,0 +1,126 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gametime/application/application.dart';
+import 'package:watch_bridge_contract/watch_bridge_contract.dart';
+
+void main() {
+  test('builds active timer notification content', () {
+    final content = buildSessionNotificationContent(
+      _projection(
+        exerciseName: 'Squats bulgares',
+        dominantTimer: _timer(label: 'Chrono étape', accumulatedMs: 134000),
+      ),
+    );
+
+    expect(content.title, 'Squats bulgares');
+    expect(content.primaryLine, '02:14');
+    expect(content.secondaryLine, 'Série 2/4');
+  });
+
+  test('builds manual score notification content', () {
+    final content = buildSessionNotificationContent(
+      _projection(
+        exerciseName: 'Lancers francs',
+        hasManualScore: true,
+        currentManualScoreValue: 8,
+      ),
+    );
+
+    expect(content.title, 'Lancers francs');
+    expect(content.primaryLine, 'Série 2/4 · 8');
+  });
+
+  test('builds rest notification content with next exercise', () {
+    final now = DateTime.utc(2026, 7, 26, 10);
+    final content = buildSessionNotificationContent(
+      _projection(
+        phase: WatchSessionPhase.restRunning,
+        exerciseName: 'Squats',
+        nextExerciseName: 'Fentes',
+        dominantTimer: _timer(
+          kind: WatchTimerKind.rest,
+          displayMode: WatchTimerDisplayMode.countdown,
+          runState: WatchTimerRunState.running,
+          accumulatedMs: 10000,
+          targetMs: 60000,
+          startedAtEpochMs: now.millisecondsSinceEpoch,
+        ),
+      ),
+      now: now.add(const Duration(seconds: 5)),
+    );
+
+    expect(content.title, 'Repos');
+    expect(content.primaryLine, '00:45 restant · Ensuite : Fentes');
+  });
+
+  test('prefixes paused content without ticking', () {
+    final content = buildSessionNotificationContent(
+      _projection(
+        phase: WatchSessionPhase.paused,
+        dominantTimer: _timer(
+          runState: WatchTimerRunState.paused,
+          accumulatedMs: 42000,
+        ),
+      ),
+      now: DateTime.utc(2026, 7, 26, 10),
+    );
+
+    expect(content.primaryLine, 'En pause · 00:42');
+  });
+
+  test('falls back to current step name without timer or score', () {
+    final content = buildSessionNotificationContent(
+      _projection(stepName: 'Gainage'),
+    );
+
+    expect(content.primaryLine, 'Gainage');
+  });
+}
+
+WatchSessionProjection _projection({
+  WatchSessionPhase phase = WatchSessionPhase.running,
+  String exerciseName = 'Pompes',
+  String? stepName,
+  WatchTimerProjection? dominantTimer,
+  bool hasManualScore = false,
+  double? currentManualScoreValue,
+  String? nextExerciseName,
+}) {
+  return WatchSessionProjection(
+    deviceSessionId: 'session-1',
+    revision: 1,
+    projectedAtEpochMs: DateTime.utc(2026, 7, 26, 10).millisecondsSinceEpoch,
+    phase: phase,
+    phoneReachable: true,
+    seriesIndex: 2,
+    seriesTotal: 4,
+    exerciseName: exerciseName,
+    stepName: stepName,
+    dominantTimer: dominantTimer,
+    primaryAction: WatchPrimaryAction.pauseSession,
+    nextExerciseName: nextExerciseName,
+    hasManualScore: hasManualScore,
+    currentManualScoreValue: currentManualScoreValue,
+    canDecrementScore: (currentManualScoreValue ?? 0) > 0,
+  );
+}
+
+WatchTimerProjection _timer({
+  WatchTimerKind kind = WatchTimerKind.step,
+  String label = 'Chrono',
+  WatchTimerDisplayMode displayMode = WatchTimerDisplayMode.elapsed,
+  WatchTimerRunState runState = WatchTimerRunState.stopped,
+  int accumulatedMs = 0,
+  int? startedAtEpochMs,
+  int? targetMs,
+}) {
+  return WatchTimerProjection(
+    kind: kind,
+    label: label,
+    displayMode: displayMode,
+    runState: runState,
+    referenceEpochMs: DateTime.utc(2026, 7, 26, 10).millisecondsSinceEpoch,
+    accumulatedMs: accumulatedMs,
+    startedAtEpochMs: startedAtEpochMs,
+    targetMs: targetMs,
+  );
+}