Add WatchConnectivity for bidirectional iOS-Watch sync

Implement real-time sync between iOS and Apple Watch apps using
WatchConnectivity framework. This replaces reliance on CloudKit
which doesn't work reliably in simulators.

- Add WatchConnectivityManager to both iOS and Watch targets
- Sync workouts, splits, exercises, and logs between devices
- Update iOS views to trigger sync on data changes
- Add onChange observer to ExerciseView for live progress updates
- Configure App Groups for shared container storage
- Add Watch app views: WorkoutLogsView, WorkoutLogListView, ExerciseProgressView

Workouts/Persistence/PersistenceController.swift

@@ -9,6 +9,9 @@ struct PersistenceController {
     // CloudKit container identifier
     static let cloudKitContainerIdentifier = "iCloud.dev.rzen.indie.Workouts"
 
+    // App Group identifier for shared storage between iOS and Watch
+    static let appGroupIdentifier = "group.dev.rzen.indie.Workouts"
+
     var viewContext: NSManagedObjectContext {
         container.viewContext
     }
@@ -57,28 +60,37 @@ struct PersistenceController {
         if inMemory {
             description.url = URL(fileURLWithPath: "/dev/null")
             description.cloudKitContainerOptions = nil
-        } else if cloudKitEnabled {
-            // Check if CloudKit is available before enabling
-            let cloudKitAvailable = FileManager.default.ubiquityIdentityToken != nil
-
-            if cloudKitAvailable {
-                // Set CloudKit container options
-                let cloudKitOptions = NSPersistentCloudKitContainerOptions(
-                    containerIdentifier: Self.cloudKitContainerIdentifier
-                )
-                description.cloudKitContainerOptions = cloudKitOptions
-            } else {
-                // CloudKit not available (not signed in, etc.)
-                description.cloudKitContainerOptions = nil
-                print("CloudKit not available - using local storage only")
+        } else {
+            // Use App Group container for shared storage between iOS and Watch
+            if let appGroupURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: Self.appGroupIdentifier) {
+                let storeURL = appGroupURL.appendingPathComponent("Workouts.sqlite")
+                description.url = storeURL
+                print("Using shared App Group store at: \(storeURL)")
             }
 
-            // Enable persistent history tracking (useful even without CloudKit)
-            description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
-            description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
-        } else {
-            // CloudKit explicitly disabled
-            description.cloudKitContainerOptions = nil
+            if cloudKitEnabled {
+                // Check if CloudKit is available before enabling
+                let cloudKitAvailable = FileManager.default.ubiquityIdentityToken != nil
+
+                if cloudKitAvailable {
+                    // Set CloudKit container options
+                    let cloudKitOptions = NSPersistentCloudKitContainerOptions(
+                        containerIdentifier: Self.cloudKitContainerIdentifier
+                    )
+                    description.cloudKitContainerOptions = cloudKitOptions
+                } else {
+                    // CloudKit not available (not signed in, etc.)
+                    description.cloudKitContainerOptions = nil
+                    print("CloudKit not available - using local storage only")
+                }
+
+                // Enable persistent history tracking (useful even without CloudKit)
+                description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
+                description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
+            } else {
+                // CloudKit explicitly disabled
+                description.cloudKitContainerOptions = nil
+            }
         }
 
         container.loadPersistentStores { storeDescription, error in