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/database.py

@@ -51,6 +51,20 @@ def _migrate():
             conn.execute(text("ALTER TABLE users ADD COLUMN custom_permissions JSON DEFAULT NULL"))
             conn.commit()
 
+        # 检查 accounts.email_imap_ssl 列是否存在
+        result = conn.execute(text("PRAGMA table_info(accounts)"))
+        columns = [row[1] for row in result]
+        if 'email_imap_ssl' not in columns:
+            # 旧数据端口993的默认True（SSL），其他端口默认False
+            conn.execute(text("ALTER TABLE accounts ADD COLUMN email_imap_ssl BOOLEAN DEFAULT 1"))
+            conn.commit()
+            # 修正旧数据中使用 111.229.206.54 的账号：端口改为143，SSL改为False
+            conn.execute(text(
+                "UPDATE accounts SET email_imap_port = 143, email_imap_ssl = 0 "
+                "WHERE email_imap_server = '111.229.206.54'"
+            ))
+            conn.commit()
+
 
 def _seed():
     """写入默认超管账号和角色。"""