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/SplashCoordinator.swift

@@ -0,0 +1,45 @@
+//
+//  SplashCoordinator.swift
+//  suixinkan
+//
+//  Created by Codex on 2026/6/29.
+//
+
+import Combine
+import Foundation
+
+@MainActor
+/// 启动页时序协调器，保证品牌页最短展示时长与冷启动 bootstrap 并行完成。
+final class SplashCoordinator: ObservableObject {
+    @Published private(set) var isFinished = false
+
+    private let minimumDisplayDuration: TimeInterval
+    private let skipsMinimumDuration: Bool
+
+    /// 创建启动页协调器，并配置最短展示时长与 UI Test 跳过策略。
+    init(
+        minimumDisplayDuration: TimeInterval = 1.5,
+        skipsMinimumDuration: Bool = AppUITestLaunchState.isRunningUITests
+    ) {
+        self.minimumDisplayDuration = minimumDisplayDuration
+        self.skipsMinimumDuration = skipsMinimumDuration
+    }
+
+    /// 并行执行 bootstrap 与最短展示时长，两者都完成后结束 Splash。
+    func start(bootstrap: @escaping () async -> Void) async {
+        guard !isFinished else { return }
+
+        async let minimumDelay: Void = waitForMinimumDisplayDuration()
+        async let bootstrapWork: Void = bootstrap()
+
+        _ = await (minimumDelay, bootstrapWork)
+        isFinished = true
+    }
+
+    /// 等待最短展示时长；UI Test 模式下直接返回。
+    private func waitForMinimumDisplayDuration() async {
+        guard !skipsMinimumDuration else { return }
+        let nanoseconds = UInt64(max(minimumDisplayDuration, 0) * 1_000_000_000)
+        try? await Task.sleep(nanoseconds: nanoseconds)
+    }
+}