feat: show recipient & AI-generated subject in summary

- AI now generates a concise subject title (not copy original)
- AI prompt includes recipient field in JSON schema
- Telegram message shows recipient and uses AI-generated title

src/tg_bot.py

@@ -23,10 +23,10 @@ def format_summary(data: dict) -> str:
     icon = _priority_icon.get(priority, "⚪")
 
     lines = [
-        f"*📧 新邮件摘要*",
+        f"*📧 {_escape(data.get('subject', '邮件摘要'))}*",
         f"━━━━━━━━━━━━━━━━━━",
+        f"*收件人:* {_escape(data.get('recipient', '未知'))}",
         f"*发件人:* {_escape(data.get('sender', '未知'))}",
-        f"*主题:* {_escape(data.get('subject', '无主题'))}",
         f"*优先级:* {icon} {priority.upper()}",
         "",
         _escape(data.get("summary", "")),