Enable iCloud sync by default, remove user toggle

- CloudKit sync is now always enabled for all users
- Remove useCloudKit setting and toggle from Settings
- Remove CloudKitSyncMonitor usage (package can be removed)
- Remove container switching logic since sync is always on
- Update SharedModelContainer defaults to enable CloudKit

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Shared/Persisence/DataController.swift

@@ -20,12 +20,8 @@ final class DataController: ObservableObject {
         container.mainContext
     }
 
-    private var useCloudKit: Bool {
-        GroupUserDefaults.groupDefaults.bool(forKey: UserDefaultsStore.Keys.useCloudKit.rawValue)
-    }
 
     // Listeners for data changes (keeping existing pattern)
-    var switchContainerListeners = [(() -> Void)]()
     private var editedDataClosure = [() -> Void]()
 
     // Computed properties for earliest/latest entries
@@ -46,19 +42,9 @@ final class DataController: ObservableObject {
     }
 
     private init() {
-        let cloudKit = GroupUserDefaults.groupDefaults.bool(forKey: UserDefaultsStore.Keys.useCloudKit.rawValue)
-        container = SharedModelContainer.createWithFallback(useCloudKit: cloudKit)
+        container = SharedModelContainer.createWithFallback(useCloudKit: true)
     }
 
-    // MARK: - Container Switching (for CloudKit toggle)
-
-    func switchContainer() {
-        save()
-        container = SharedModelContainer.createWithFallback(useCloudKit: useCloudKit)
-        for listener in switchContainerListeners {
-            listener()
-        }
-    }
 
     // MARK: - Listener Management