修复IMAP连接：支持非SSL端口143

- IMAP服务器 111.229.206.54 只开放143端口（非SSL），993不通
- 默认配置改为端口143、ssl=False
- EmailVerifier 增加 use_ssl 参数，支持 IMAP4 和 IMAP4_SSL
- Account 模型增加 email_imap_ssl 字段
- 数据库迁移：新增列 + 修正旧数据端口和SSL设置
- 导入账号时自动填充 ssl 配置

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/backend/services/login_service.py

@@ -122,6 +122,7 @@ class LoginBatchRunner:
                     email_password=acc_info["email_password"],
                     email_imap_server=acc_info["email_imap_server"] or "",
                     email_imap_port=acc_info["email_imap_port"] or 993,
+                    email_imap_ssl=acc_info["email_imap_ssl"],
                 )
 
                 loginer = DouyuLogin(
@@ -205,6 +206,7 @@ class LoginBatchRunner:
                     "email_password": acc.email_password,
                     "email_imap_server": acc.email_imap_server or "",
                     "email_imap_port": acc.email_imap_port or 993,
+                    "email_imap_ssl": acc.email_imap_ssl if acc.email_imap_ssl is not None else True,
                 },
             })