fix: process one queued email per poll cycle to keep callbacks responsive

main.py

@@ -107,14 +107,14 @@ def _tg_worker(cfg):
         except Exception as e:
             logger.error(f"TG 轮询错误: {e}", exc_info=True)
 
-        while _running:
+        # 每轮只处理一封待发邮件，然后立刻回去 poll Telegram
         try:
             info = _tg_queue.get_nowait()
             tg_send_and_mark(cfg, info)
             uid_str = info["uid"].decode("utf-8", errors="replace") if isinstance(info["uid"], bytes) else str(info["uid"])
             mark_sent(uid_str)
         except queue_module.Empty:
-                break
+            pass
         except Exception as e:
             logger.error(f"TG 发送失败: {e}", exc_info=True)
             try:
@@ -124,7 +124,7 @@ def _tg_worker(cfg):
                 pass
 
         if _running:
-            _shutdown_event.wait(1)
+            _shutdown_event.wait(0.2)
 
 
 def main():