fix(ios): APIClient 401 错误码传递到 AuthManager，完成错误码分支闭环

- notifyTokenExpired 接受 errorCode 参数，通过 Notification userInfo 传递
- 401 响应提取 errorCode 后传给 notifyTokenExpired
- AuthManager 观察者从 userInfo 读取 errorCode，调用 applyErrorCode
- handleUnauthorized 根据 errorCode 切换精确状态（disabled/deleted/expired）
- restoreSession 冷启动也检查 errorCode，禁用/删除用户不尝试 refresh

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AIStudyApp/AIStudyApp/Core/Auth/AuthManager.swift

@@ -30,9 +30,10 @@ final class AuthManager: ObservableObject {
     init() {
         tokenExpiredObserver = NotificationCenter.default.addObserver(
             forName: .tokenExpired, object: nil, queue: .main
-        ) { [weak self] _ in
+        ) { [weak self] notification in
+            let errorCode = notification.userInfo?["errorCode"] as? String
             Task { @MainActor [weak self] in
-                self?.handleUnauthorized()
+                self?.handleUnauthorized(errorCode: errorCode)
             }
         }
     }
@@ -59,6 +60,14 @@ final class AuthManager: ObservableObject {
             let _: UserProfileResponse = try await APIClient.shared.request("/users/me")
             session = .authenticated
         } catch {
+            // 如果 /users/me 返回了特定错误码（禁用/删除），直接切状态，不尝试 refresh
+            if let apiError = error as? APIError, let code = apiError.errorCode {
+                await APIClient.shared.setToken(nil)
+                KeychainHelper.clear()
+                applyErrorCode(code)
+                return
+            }
+
             session = .refreshing
             if let refreshed = await tryRefresh() {
                 await APIClient.shared.setToken(refreshed.accessToken)
@@ -120,13 +129,17 @@ final class AuthManager: ObservableObject {
 
     // MARK: - Private
 
-    private func handleUnauthorized() {
+    private func handleUnauthorized(errorCode: String? = nil) {
         Task {
             await APIClient.shared.setToken(nil)
             KeychainHelper.clear()
+            if let code = errorCode {
+                applyErrorCode(code)
+            } else {
                 session = .unauthenticated
             }
         }
+    }
 
     private func tryRefresh() async -> AuthResponse? {
         guard let refreshToken = KeychainHelper.getRefreshToken() else { return nil }

AIStudyApp/AIStudyApp/Core/Network/APIClient.swift

@@ -69,10 +69,12 @@ actor APIClient {
                 self.token = newToken
                 return try await performRequest(path, method: method, body: body, queryItems: queryItems, isRetry: true)
             }
-            await notifyTokenExpired()
+            let info = extractErrorInfo(data)
+            await notifyTokenExpired(errorCode: info.errorCode)
             throw decodeServerError(data, fallback: APIError.unauthorized)
         case 401:
-            throw decodeServerError(data, fallback: APIError.unauthorized)
+            let info = extractErrorInfo(data)
+            throw APIError.serverError(info.message ?? "未授权", code: info.errorCode)
         case 400..<500:
             let msg = String(data: data, encoding: .utf8) ?? ""
             throw APIError.serverError(msg)
@@ -99,9 +101,13 @@ actor APIClient {
         }
     }
 
-    private func notifyTokenExpired() async {
+    private func notifyTokenExpired(errorCode: String? = nil) async {
+        var userInfo: [AnyHashable: Any]? = nil
+        if let code = errorCode {
+            userInfo = ["errorCode": code]
+        }
         await MainActor.run {
-            NotificationCenter.default.post(name: .tokenExpired, object: nil)
+            NotificationCenter.default.post(name: .tokenExpired, object: nil, userInfo: userInfo)
         }
     }