Add networking layer and wire up v9 login flow with unit tests.

Introduce APIClient/AuthAPI, complete login with multi-account selection, and polish the login card UI with shadow and keyboard dismiss.

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

suixinkanTests/APIClientTests.swift

@@ -0,0 +1,99 @@
+//
+//  APIClientTests.swift
+//  suixinkanTests
+//
+
+import XCTest
+@testable import suixinkan
+
+@MainActor
+/// APIClient 测试，覆盖 Envelope 解包、业务码失败和 token 注入。
+final class APIClientTests: XCTestCase {
+    func testSendDecodesSuccessEnvelope() async throws {
+        let responseData = try TestJSON.envelope(data: AppConfigResponse(enableRegister: true))
+        let session = MockURLSession(responses: [responseData])
+        let client = APIClient(
+            environment: .testing,
+            session: session,
+            appVersion: "1.0.0",
+            osType: "iOS"
+        )
+
+        let config: AppConfigResponse = try await client.send(
+            APIRequest<AppConfigResponse>(method: .get, path: "/api/app/config")
+        )
+
+        XCTAssertTrue(config.enableRegister)
+        XCTAssertEqual(session.requests.count, 1)
+        XCTAssertEqual(session.requests[0].value(forHTTPHeaderField: "X-APP-VERSION"), "1.0.0")
+        XCTAssertEqual(session.requests[0].value(forHTTPHeaderField: "X-OS-TYPE"), "iOS")
+    }
+
+    func testSendInjectsTokenHeaderWhenProviderBound() async throws {
+        let responseData = try TestJSON.envelope(data: AppConfigResponse(enableRegister: false))
+        let session = MockURLSession(responses: [responseData])
+        let client = APIClient(environment: .testing, session: session)
+        client.bindAuthTokenProvider { "test-token-abc" }
+
+        _ = try await client.send(APIRequest<AppConfigResponse>(method: .get, path: "/api/app/config"))
+
+        XCTAssertEqual(session.requests[0].value(forHTTPHeaderField: "token"), "test-token-abc")
+    }
+
+    func testSendThrowsServerCodeErrorForBusinessFailure() async throws {
+        let responseData = try TestJSON.errorEnvelope(code: 100001, msg: "密码错误")
+        let session = MockURLSession(responses: [responseData])
+        let client = APIClient(environment: .testing, session: session)
+
+        do {
+            let _: AppConfigResponse = try await client.send(
+                APIRequest<AppConfigResponse>(method: .get, path: "/api/app/config")
+            )
+            XCTFail("业务码失败时应抛出错误")
+        } catch let error as APIError {
+            guard case let .serverCode(code, message) = error else {
+                return XCTFail("期望 serverCode，实际为 \(error)")
+            }
+            XCTAssertEqual(code, 100001)
+            XCTAssertEqual(message, "密码错误")
+        }
+    }
+
+    func testSendThrowsHTTPStatusError() async throws {
+        let session = MockURLSession(results: [
+            .success((
+                Data(),
+                HTTPURLResponse(
+                    url: URL(string: "https://api-test.zhifly.cn/mock")!,
+                    statusCode: 500,
+                    httpVersion: nil,
+                    headerFields: nil
+                )!
+            )),
+        ])
+        let client = APIClient(environment: .testing, session: session)
+
+        do {
+            let _: AppConfigResponse = try await client.send(
+                APIRequest<AppConfigResponse>(method: .get, path: "/api/app/config")
+            )
+            XCTFail("HTTP 500 时应抛出错误")
+        } catch let error as APIError {
+            guard case let .httpStatus(statusCode, _) = error else {
+                return XCTFail("期望 httpStatus，实际为 \(error)")
+            }
+            XCTAssertEqual(statusCode, 500)
+        }
+    }
+
+    func testTokenInvalidCodePostsSessionDidExpireNotification() async {
+        let expectation = expectation(forNotification: NotificationName.sessionDidExpire, object: nil)
+        let responseData = try! TestJSON.errorEnvelope(code: 180024, msg: "token 失效")
+        let session = MockURLSession(responses: [responseData])
+        let client = APIClient(environment: .testing, session: session)
+
+        _ = try? await client.send(APIRequest<AppConfigResponse>(method: .get, path: "/api/app/config"))
+
+        await fulfillment(of: [expectation], timeout: 1)
+    }
+}