Add reminder notifications to schedules

- ScheduleDocument/Schedule gain optional reminderMinutes (minutes from
  midnight; decode-compatible, no schema bump)
- New Workout form gets a Reminder section (toggle + time picker, hidden
  for Now; footer warns when notifications are denied)
- ReminderPlanner (pure, tested) derives notification triggers: daily
  repeating, per-weekday repeating for fixed days, one-shot for once
- ReminderScheduler resyncs pending requests from the cache on every
  change, multiplexed onto onCacheChanged after the watch push; asks
  notification permission only once a reminder actually exists

Workouts/AppServices.swift

@@ -19,6 +19,10 @@ final class AppServices {
     let workoutLauncher = WorkoutLauncher()
     let workoutHealthDeleter = WorkoutHealthDeleter()
 
+    /// Keeps pending local notifications in sync with the schedules' reminder times
+    /// (an idempotent full resync on every cache change).
+    let reminderScheduler: ReminderScheduler
+
     /// Speaks exercise instructions aloud (library Speak button + hands-free workout cues).
     /// Shared so a new exercise's cue cancels whatever the last screen was still saying.
     let speechAnnouncer = SpeechAnnouncer()
@@ -43,6 +47,7 @@ final class AppServices {
         let liveRunState = LiveRunState()
         self.liveRunState = liveRunState
         self.watchBridge = PhoneConnectivityBridge(container: container, syncEngine: syncEngine, liveRunState: liveRunState)
+        self.reminderScheduler = ReminderScheduler(container: container)
         // Launch the wrist session only when a run actually begins (the first
         // exercise leaves `.notStarted` on the phone) — creating a workout alone is
         // just a peek and must not start anything on the watch. Watch-originated
@@ -70,6 +75,16 @@ final class AppServices {
             await self.liveActivity.endStaleActivities()
             await self.syncEngine.connect()
             self.watchBridge.activate()
+            // `activate()` just claimed `onCacheChanged` for the watch push — multiplex
+            // rather than replace, so reminder reconciliation rides the same signal.
+            let watchPush = self.syncEngine.onCacheChanged
+            self.syncEngine.onCacheChanged = { [weak self] in
+                watchPush?()
+                self?.reminderScheduler.scheduleReconcile()
+            }
+            // Initial post-bootstrap resync (covers changes that happened while
+            // the app wasn't running — e.g. schedules edited on another device).
+            self.reminderScheduler.scheduleReconcile()
             // Past the iCloud gate: request the workout-share scope so the user can still
             // delete legacy phone-estimate workouts from Health when deleting them here.
             self.workoutHealthDeleter.authorizeIfNeeded()