fix(mobile-next): 登录失败改为顶部 toast，2 秒后自动消失

改 company_login_page.dart 与 company_login_logic.dart。
保留「工号或密码不正确」「网络异常，请稍后重试」；去掉按钮下方常驻错误字。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

mobile-next/lib/company/auth/company_login_logic.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 import 'package:openim/core/controller/im_controller.dart';
@@ -15,12 +17,14 @@ class CompanyLoginLogic extends GetxController {
   final staffError = RxnString();
   final pwdError = RxnString();
   final toast = RxnString();
+  Timer? _toastTimer;
 
   final _auth = AuthApi();
   final _im = Get.find<IMController>();
 
   @override
   void onClose() {
+    _toastTimer?.cancel();
     staffCtrl.dispose();
     pwdCtrl.dispose();
     super.onClose();
@@ -28,6 +32,14 @@ class CompanyLoginLogic extends GetxController {
 
   void toggleObscure() => obscure.toggle();
 
+  void _showToast(String msg) {
+    toast.value = msg;
+    _toastTimer?.cancel();
+    _toastTimer = Timer(const Duration(seconds: 2), () {
+      toast.value = null;
+    });
+  }
+
   Future<void> submit() async {
     if (submitting.value) return;
     final staffNo = staffCtrl.text.trim();
@@ -58,10 +70,10 @@ class CompanyLoginLogic extends GetxController {
       Get.find<CacheController>().resetCache();
       AppNavigator.startMain(conversations: conversations);
     } on AuthException catch (e) {
-      toast.value = e.network ? '网络异常，请稍后重试' : '工号或密码不正确';
+      _showToast(e.network ? '网络异常，请稍后重试' : '工号或密码不正确');
     } catch (e, s) {
       Logger.print('company login e: $e $s');
-      toast.value = '网络异常，请稍后重试';
+      _showToast('网络异常，请稍后重试');
     } finally {
       submitting.value = false;
     }