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/AppConfigTests.swift

@@ -0,0 +1,87 @@
+//
+//  AppConfigTests.swift
+//  suixinkanTests
+//
+//  Created by Codex on 2026/6/29.
+//
+
+import XCTest
+@testable import suixinkan
+
+@MainActor
+/// App 配置接口测试，覆盖 API 请求路径和登录页配置加载行为。
+final class AppConfigTests: XCTestCase {
+    /// 测试 App 配置接口使用正确路径并解析 enable_register 字段。
+    func testAppConfigAPIRequestsConfigEndpoint() async throws {
+        let response = """
+        {
+          "code": 100000,
+          "msg": "success",
+          "data": {
+            "enable_register": true
+          }
+        }
+        """.data(using: .utf8)!
+        let session = AppConfigURLSession(responses: [response])
+        let api = AppConfigAPI(client: APIClient(session: session))
+
+        let config = try await api.fetchAppConfig()
+
+        XCTAssertTrue(config.enableRegister)
+        let request = try XCTUnwrap(session.requests.first)
+        XCTAssertEqual(request.httpMethod, "GET")
+        XCTAssertEqual(request.url?.path, "/api/app/config")
+    }
+
+    /// 测试登录页加载 App 配置成功时会更新 enableRegister。
+    func testLoginViewModelLoadAppConfigUpdatesEnableRegister() async throws {
+        let response = """
+        {
+          "code": 100000,
+          "msg": "success",
+          "data": {
+            "enable_register": true
+          }
+        }
+        """.data(using: .utf8)!
+        let session = AppConfigURLSession(responses: [response])
+        let api = AppConfigAPI(client: APIClient(session: session))
+        let viewModel = LoginViewModel()
+
+        await viewModel.loadAppConfig(appConfigAPI: api)
+
+        XCTAssertTrue(viewModel.enableRegister)
+    }
+
+    /// 测试登录页加载 App 配置失败时保持默认值。
+    func testLoginViewModelLoadAppConfigKeepsDefaultOnFailure() async {
+        let session = AppConfigURLSession(responses: [Data()])
+        let api = AppConfigAPI(client: APIClient(session: session))
+        let viewModel = LoginViewModel()
+
+        await viewModel.loadAppConfig(appConfigAPI: api)
+
+        XCTAssertFalse(viewModel.enableRegister)
+    }
+}
+
+/// App 配置测试用 URLSession 替身，按顺序返回预设响应。
+private final class AppConfigURLSession: URLSessionProtocol {
+    private var responses: [Data]
+    private(set) var requests: [URLRequest] = []
+
+    /// 初始化顺序响应。
+    init(responses: [Data]) {
+        self.responses = responses
+    }
+
+    /// 记录请求并返回下一份响应。
+    func data(for request: URLRequest) async throws -> (Data, URLResponse) {
+        requests.append(request)
+        let data = responses.isEmpty ? Data() : responses.removeFirst()
+        return (
+            data,
+            HTTPURLResponse(url: request.url!, statusCode: 200, httpVersion: nil, headerFields: nil)!
+        )
+    }
+}