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

Shared/Model/Documents.swift

@@ -377,6 +377,10 @@ struct ScheduleDocument: Codable, Sendable, Equatable, Identifiable {
     var recurrence: String    // ScheduleRecurrence raw value
     var weekdays: [Int]?      // Calendar weekday numbers 1 (Sun) – 7 (Sat); .fixedDays only
     var date: Date? = nil     // the one-off day; .once only
+    /// Reminder time as minutes from midnight (local wall-clock, 0–1439); nil = no
+    /// reminder. Optional addition — decode-compatible, deliberately NOT schema-bumped
+    /// (an older app dropping it on rewrite loses only a notification preference).
+    var reminderMinutes: Int? = nil
     var order: Int
     var createdAt: Date
     var updatedAt: Date

Shared/Model/Entities.swift

@@ -318,13 +318,15 @@ final class Schedule {
     var recurrenceRaw: String = ScheduleRecurrence.daily.rawValue
     var weekdays: [Int]?
     var date: Date?
+    /// Reminder time as minutes from midnight (local wall-clock); nil = no reminder.
+    var reminderMinutes: Int?
     var order: Int = 0
     var createdAt: Date = Date()
     var updatedAt: Date = Date()
     var jsonRelativePath: String = ""
 
     init(id: String, routineID: String, routineName: String, goalRaw: String?,
-         recurrenceRaw: String, weekdays: [Int]?, date: Date? = nil,
+         recurrenceRaw: String, weekdays: [Int]?, date: Date? = nil, reminderMinutes: Int? = nil,
          order: Int, createdAt: Date, updatedAt: Date, jsonRelativePath: String) {
         self.id = id
         self.routineID = routineID
@@ -333,6 +335,7 @@ final class Schedule {
         self.recurrenceRaw = recurrenceRaw
         self.weekdays = weekdays
         self.date = date
+        self.reminderMinutes = reminderMinutes
         self.order = order
         self.createdAt = createdAt
         self.updatedAt = updatedAt

Shared/Model/Mappers.swift

@@ -92,7 +92,7 @@ extension ScheduleDocument {
                   routineID: schedule.routineID, routineName: schedule.routineName,
                   goal: schedule.goalRaw, recurrence: schedule.recurrenceRaw,
                   weekdays: schedule.weekdays,
-                  date: schedule.date,
+                  date: schedule.date, reminderMinutes: schedule.reminderMinutes,
                   order: schedule.order, createdAt: schedule.createdAt, updatedAt: schedule.updatedAt)
     }
 }
@@ -255,7 +255,7 @@ enum CacheMapper {
         } else {
             schedule = Schedule(id: doc.id, routineID: doc.routineID, routineName: doc.routineName,
                                 goalRaw: doc.goal, recurrenceRaw: doc.recurrence, weekdays: doc.weekdays,
-                                date: doc.date, order: doc.order,
+                                date: doc.date, reminderMinutes: doc.reminderMinutes, order: doc.order,
                                 createdAt: doc.createdAt, updatedAt: doc.updatedAt,
                                 jsonRelativePath: relativePath)
             context.insert(schedule)
@@ -266,6 +266,7 @@ enum CacheMapper {
         schedule.recurrenceRaw = doc.recurrence
         schedule.weekdays = doc.weekdays
         schedule.date = doc.date
+        schedule.reminderMinutes = doc.reminderMinutes
         schedule.order = doc.order
         schedule.createdAt = doc.createdAt
         schedule.updatedAt = doc.updatedAt