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/tg_bot.py

@@ -22,7 +22,7 @@ _conversations: dict[int, dict] = {}
 @retry()
 def send_summary(tg_cfg: TelegramConfig, chat_id: str, summary_text: str,
                  summary_data: dict, original_body: str, account_idx: int,
-                 original_sender: str = "") -> int:
+                 original_sender: str = "", original_recipient: str = "") -> int:
     can_reply = summary_data.get("can_reply", True)
     result = _tg_req(tg_cfg, "sendMessage", {
         "chat_id": chat_id,
@@ -36,6 +36,7 @@ def send_summary(tg_cfg: TelegramConfig, chat_id: str, summary_text: str,
         "summary_data": summary_data,
         "original_body": original_body[:10000],
         "original_sender": original_sender or summary_data.get("sender", ""),
+        "original_recipient": original_recipient or summary_data.get("recipient", ""),
         "account_idx": account_idx,
         "sender": summary_data.get("sender", ""),
         "subject": summary_data.get("subject", ""),