feat: AI并行处理 + 修复邮件丢失

- _ai_processor 改用 ThreadPoolExecutor(5 workers) 并行调用AI
- _tg_worker 每轮排空所有待发TG消息(原来每轮只取1条)
- fetch_unseen_emails 单封FETCH失败不再丢弃整个批次，跳过继续

src/email_client.py

@@ -115,24 +115,28 @@ def fetch_unseen_emails(account: EmailAccount) -> list[Email]:
     emails = []
 
     for uid in uids:
-        _, msg_data = conn.uid("FETCH", uid, "RFC822")
-        if msg_data[0] is None:
-            logger.warning("UID %s FETCH 返回空，跳过", uid)
+        try:
+            _, msg_data = conn.uid("FETCH", uid, "RFC822")
+            if msg_data[0] is None:
+                logger.warning("UID %s FETCH 返回空，跳过", uid)
+                continue
+            raw_email = msg_data[0][1]
+            msg = email.message_from_bytes(raw_email)
+
+            subject = _decode_str(msg.get("Subject", ""))
+            sender = _decode_address_header(msg.get("From", ""))
+            recipient = _decode_address_header(msg.get("To", ""))
+            reply_to = _decode_address_header(msg.get("Reply-To", ""))
+            date_str = msg.get("Date", "")
+            body = _get_text_from_msg(msg)
+            body_len = len(body)
+
+            logger.info("  邮件: [%s] from=%s to=%s reply-to=%s (%d 字符)", subject, sender, recipient, reply_to, body_len)
+            emails.append(Email(uid=uid, subject=subject, sender=sender, recipient=recipient,
+                                body=body, date=date_str, reply_to=reply_to, account_email=account.username))
+        except Exception as e:
+            logger.error("UID %s FETCH 失败，跳过: %s", uid, e)
             continue
-        raw_email = msg_data[0][1]
-        msg = email.message_from_bytes(raw_email)
-
-        subject = _decode_str(msg.get("Subject", ""))
-        sender = _decode_address_header(msg.get("From", ""))
-        recipient = _decode_address_header(msg.get("To", ""))
-        reply_to = _decode_address_header(msg.get("Reply-To", ""))
-        date_str = msg.get("Date", "")
-        body = _get_text_from_msg(msg)
-        body_len = len(body)
-
-        logger.info("  邮件: [%s] from=%s to=%s reply-to=%s (%d 字符)", subject, sender, recipient, reply_to, body_len)
-        emails.append(Email(uid=uid, subject=subject, sender=sender, recipient=recipient,
-                            body=body, date=date_str, reply_to=reply_to, account_email=account.username))
 
     conn.logout()
     logger.info("共获取 %d 封新邮件", len(emails))