fix 429 error for openrouter api

src/telegram_bot/telegram_bot_service.py

@@ -1,3 +1,4 @@
+import asyncio
 from typing import Any
 from datetime import datetime, timedelta
 import time
@@ -265,6 +266,7 @@ class TelegramBotService:
             elapsed = time.perf_counter() - start_time
             main_logger.info(f"Processing time: {elapsed:.2f} seconds")
             await self.send_message_via_proxy(chat_id, f"LLM Response for {news.get('headline', 'No headline')}: {response}")
+            await asyncio.sleep(4)  # Rate limit to avoid hitting Openrouter API limits
 
     async def news_feed_pooling_by_ticker(
             self, ticker: str, chat_id: int, text: str | None, user_name: str