同步 Android 启动页到 iOS，并在冷启动期间静默恢复登录态。

新增 SplashView、SplashCoordinator 与 Launch Screen 资源，移除冷启动 Lottie；LoginView 加载 App 配置。同时将 token 存储迁移至 UserDefaults，并更新相关测试与文档。

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

suixinkan/App/RootView.swift

@@ -47,6 +47,8 @@ struct RootView: View {
     @State private var cooperationOrderAPI: CooperationOrderAPI
     @State private var authSessionCoordinator: AuthSessionCoordinator
     @State private var sessionBootstrapper: SessionBootstrapper
+    @StateObject private var splashCoordinator = SplashCoordinator()
+    @State private var appConfigAPI: AppConfigAPI
 
     /// 初始化网络客户端和业务 API，确保它们共享同一个 token provider。
     init() {
@@ -56,6 +58,7 @@ struct RootView: View {
         _snapshotStore = State(initialValue: snapshotStore)
         _apiClient = State(initialValue: apiClient)
         _authAPI = State(initialValue: AuthAPI(client: apiClient))
+        _appConfigAPI = State(initialValue: AppConfigAPI(client: apiClient))
         _profileAPI = State(initialValue: ProfileAPI(client: apiClient))
         let uploadAPI = UploadAPI(client: apiClient)
         _uploadAPI = State(initialValue: uploadAPI)
@@ -97,7 +100,15 @@ struct RootView: View {
     }
 
     var body: some View {
-        rootContent
+        ZStack {
+            rootContent
+
+            if !splashCoordinator.isFinished {
+                SplashView()
+                    .transition(.opacity)
+                    .zIndex(1)
+            }
+        }
             .globalToastOverlay()
             .globalLoadingOverlay(loadingCenter: globalLoading)
             .environmentObject(appSession)
@@ -110,6 +121,7 @@ struct RootView: View {
             .environment(\.accountSnapshotStore, snapshotStore)
             .environment(\.apiClient, apiClient)
             .environment(\.authAPI, authAPI)
+            .environment(\.appConfigAPI, appConfigAPI)
             .environment(\.profileAPI, profileAPI)
             .environment(\.uploadAPI, uploadAPI)
             .environment(\.ossUploadService, ossUploadService)
@@ -139,7 +151,7 @@ struct RootView: View {
             .task {
                 apiClient.bindAuthTokenProvider { appSession.token }
                 PushNotificationManager.shared.configure(api: pushAPI, session: appSession, router: appRouter)
-                await globalLoading.withLoading {
+                await splashCoordinator.start {
                     await sessionBootstrapper.restore(
                         appSession: appSession,
                         accountContext: accountContext,