feat: 集成 Apple Sign-In + iOS 上线准备

- 后端新增 Apple 登录端点 /api/auth/apple-login
- 新增 AppleTokenValidator 验证 IdentityToken
- User 实体添加 AppleUserId 字段，Phone 改为可空
- 前端添加 sign_in_with_apple 依赖和 Apple 登录按钮
- 统一 Bundle ID 为 com.datalumina.YYA，显示名称为小脉健康
- 配置 DEVELOPMENT_TEAM 和 Sign in with Apple Entitlements
- 补充 NSCamera/NSPhotoLibrary 权限描述
- 生产 API 地址改为 https://erpapi.datalumina.cn/xiaomai
- Flutter 升级至 3.44.6 / Dart 3.12.2

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

health_app/ios/Runner/AppDelegate.swift

@@ -2,12 +2,15 @@ import Flutter
 import UIKit
 
 @main
-@objc class AppDelegate: FlutterAppDelegate {
+@objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate {
   override func application(
     _ application: UIApplication,
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
   ) -> Bool {
-    GeneratedPluginRegistrant.register(with: self)
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }
+
+  func didInitializeImplicitFlutterEngine(_ engineBridge: FlutterImplicitEngineBridge) {
+    GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
+  }
 }