feat(itinerary): add custom itinerary items with drag-to-reorder

- Add CustomItineraryItem domain model with sortOrder for ordering
- Add CKCustomItineraryItem CloudKit wrapper for persistence
- Create CustomItemService for CRUD operations
- Create CustomItemSubscriptionService for real-time sync
- Add AppDelegate for push notification handling
- Add AddItemSheet for creating/editing items
- Add CustomItemRow with drag handle
- Update TripDetailView with continuous vertical timeline
- Enable drag-to-reorder using .draggable/.dropDestination
- Add inline "Add" buttons after games and travel segments

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

SportsTime/Core/Services/AppDelegate.swift

@@ -0,0 +1,48 @@
+//
+//  AppDelegate.swift
+//  SportsTime
+//
+//  Handles push notification registration and CloudKit subscription notifications
+//
+
+import UIKit
+import CloudKit
+import UserNotifications
+
+class AppDelegate: NSObject, UIApplicationDelegate {
+
+    func application(
+        _ application: UIApplication,
+        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil
+    ) -> Bool {
+        // Register for remote notifications (required for CloudKit subscriptions)
+        application.registerForRemoteNotifications()
+        return true
+    }
+
+    func application(
+        _ application: UIApplication,
+        didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data
+    ) {
+        print("📡 [Push] Registered for remote notifications")
+    }
+
+    func application(
+        _ application: UIApplication,
+        didFailToRegisterForRemoteNotificationsWithError error: Error
+    ) {
+        print("📡 [Push] Failed to register: \(error.localizedDescription)")
+    }
+
+    func application(
+        _ application: UIApplication,
+        didReceiveRemoteNotification userInfo: [AnyHashable: Any],
+        fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void
+    ) {
+        // Handle CloudKit subscription notification
+        Task {
+            await CustomItemSubscriptionService.shared.handleRemoteNotification(userInfo: userInfo)
+            completionHandler(.newData)
+        }
+    }
+}