fix: resolve all flake8 lint errors (118 → 0)

src/api/mail_routes.py

@@ -9,7 +9,7 @@ from __future__ import annotations
 import json
 from datetime import datetime
 from pathlib import Path
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, Optional
 
 from fastapi import APIRouter, HTTPException, Query
 
@@ -36,6 +36,7 @@ def _get_valid_agents() -> set:
     # fallback：硬编码
     return {"zhangfei-dev", "guanyu-dev", "zhaoyun-data", "jiangwei-infra", "pangtong-fujunshi", "simayi-challenger"}
 
+
 router = APIRouter(prefix="/api/mail", tags=["mail"])
 
 MAIL_PROJECT_ID = "_mail"
@@ -222,7 +223,7 @@ async def send_mail(body: Dict[str, Any]):
 
         # A8: 只有原邮件的双方能回复（严格 1 对 1）
         if from_agent not in (orig_from, orig_to):
-            raise HTTPException(400, f"只有邮件的发送者或接收者可以回复")
+            raise HTTPException(400, "只有邮件的发送者或接收者可以回复")
 
         # A6/A7: 自动纠正 to → 原邮件发件者
         to_agent = body.get("to", "").strip()