feat: 收件人/发件人改用邮件原始头数据

- sender 从 decode 改为使用原始 From 头
- 新增 recipient 字段，使用原始 To 头
- 移除 ai_process 中对 acct.username 的依赖

src/email_client.py

@@ -11,10 +11,11 @@ logger = logging.getLogger(__name__)
 
 
 class Email:
-    def __init__(self, uid: bytes, subject: str, sender: str, body: str, date: str):
+    def __init__(self, uid: bytes, subject: str, sender: str, recipient: str, body: str, date: str):
         self.uid = uid
         self.subject = subject
         self.sender = sender
+        self.recipient = recipient
         self.body = body
         self.date = date
 
@@ -102,13 +103,14 @@ def fetch_unseen_emails(account: EmailAccount) -> list[Email]:
         msg = email.message_from_bytes(raw_email)
 
         subject = _decode_str(msg.get("Subject", ""))
-        sender = _decode_str(msg.get("From", ""))
+        sender = msg.get("From", "")
+        recipient = msg.get("To", "")
         date_str = msg.get("Date", "")
         body = _get_text_from_msg(msg)
         body_len = len(body)
 
-        logger.info("  邮件: [%s] %s <%s> (%d 字符)", subject, sender, date_str, body_len)
-        emails.append(Email(uid=uid, subject=subject, sender=sender, body=body, date=date_str))
+        logger.info("  邮件: [%s] from=%s to=%s (%d 字符)", subject, sender, recipient, body_len)
+        emails.append(Email(uid=uid, subject=subject, sender=sender, recipient=recipient, body=body, date=date_str))
 
     conn.logout()
     logger.info("共获取 %d 封新邮件", len(emails))