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>

suixinkan/DataStore/AppStore.swift

@@ -13,6 +13,8 @@ final class AppStore {
 
     private enum Key {
         static let token = "key_in_token"
+        static let lastLoginUsername = "key_last_login_username"
+        static let privacyAgreementAccepted = "key_privacy_agreement_accepted"
     }
 
     private let defaults: UserDefaults
@@ -27,6 +29,24 @@ final class AppStore {
         set { defaults.set(newValue, forKey: Key.token) }
     }
 
+    /// 上次登录手机号，用于登录页恢复。
+    var lastLoginUsername: String? {
+        get { defaults.string(forKey: Key.lastLoginUsername) }
+        set {
+            if let newValue {
+                defaults.set(newValue, forKey: Key.lastLoginUsername)
+            } else {
+                defaults.removeObject(forKey: Key.lastLoginUsername)
+            }
+        }
+    }
+
+    /// 是否已同意隐私协议。
+    var privacyAgreementAccepted: Bool {
+        get { defaults.bool(forKey: Key.privacyAgreementAccepted) }
+        set { defaults.set(newValue, forKey: Key.privacyAgreementAccepted) }
+    }
+
     /// Token 非空视为已登录。
     var isLoggedIn: Bool {
         !token.isEmpty