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>

suixinkanTests/SplashCoordinatorTests.swift

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+//
+//  SplashCoordinatorTests.swift
+//  suixinkanTests
+//
+//  Created by Codex on 2026/6/29.
+//
+
+import XCTest
+@testable import suixinkan
+
+@MainActor
+/// 启动页协调器测试，覆盖最短展示时长、bootstrap 并行和 UI Test 跳过策略。
+final class SplashCoordinatorTests: XCTestCase {
+    /// 测试 bootstrap 完成后仍需等待最短展示时长。
+    func testStartWaitsForMinimumDisplayDuration() async {
+        let coordinator = SplashCoordinator(minimumDisplayDuration: 0.2, skipsMinimumDuration: false)
+        let startedAt = Date()
+
+        await coordinator.start {
+            try? await Task.sleep(nanoseconds: 10_000_000)
+        }
+
+        XCTAssertTrue(coordinator.isFinished)
+        XCTAssertGreaterThanOrEqual(Date().timeIntervalSince(startedAt), 0.19)
+    }
+
+    /// 测试 bootstrap 耗时超过最短展示时长时，以 bootstrap 完成时间为准。
+    func testStartWaitsForSlowBootstrap() async {
+        let coordinator = SplashCoordinator(minimumDisplayDuration: 0.05, skipsMinimumDuration: false)
+        let startedAt = Date()
+
+        await coordinator.start {
+            try? await Task.sleep(nanoseconds: 150_000_000)
+        }
+
+        XCTAssertTrue(coordinator.isFinished)
+        XCTAssertGreaterThanOrEqual(Date().timeIntervalSince(startedAt), 0.14)
+    }
+
+    /// 测试 UI Test 模式会跳过最短展示时长。
+    func testStartSkipsMinimumDurationWhenRequested() async {
+        let coordinator = SplashCoordinator(minimumDisplayDuration: 1.0, skipsMinimumDuration: true)
+        let startedAt = Date()
+
+        await coordinator.start {
+            try? await Task.sleep(nanoseconds: 10_000_000)
+        }
+
+        XCTAssertTrue(coordinator.isFinished)
+        XCTAssertLessThan(Date().timeIntervalSince(startedAt), 0.2)
+    }
+
+    /// 测试重复调用 start 不会重置已完成状态。
+    func testStartIsIdempotentAfterFinished() async {
+        let coordinator = SplashCoordinator(minimumDisplayDuration: 0, skipsMinimumDuration: true)
+        var bootstrapCount = 0
+
+        await coordinator.start {
+            bootstrapCount += 1
+        }
+        await coordinator.start {
+            bootstrapCount += 1
+        }
+
+        XCTAssertTrue(coordinator.isFinished)
+        XCTAssertEqual(bootstrapCount, 1)
+    }
+}