Add APNs push notification registration and payload routing.

Introduce AppDelegate, explicit Info.plist and entitlements, and wire PushNotificationManager into login lifecycle for device token upload and notification handling.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan/App/suixinkanApp.swift

@@ -10,6 +10,8 @@ import SwiftUI
 /// 应用入口实体，负责把 SwiftUI 根视图挂载到主窗口。
 @main
 struct suixinkanApp: App {
+    @UIApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
+
     var body: some Scene {
         WindowGroup {
             RootView()