chore: Add requirements.txt and EXCHANGE_API_KEY startup warning.

SubMind.py

@@ -1580,6 +1580,9 @@ def main():
         logger.critical("TELEGRAM_TOKEN 环境变量未设置！")
         return
     
+    if not EXCHANGE_API_KEY:
+        logger.info("未配置 EXCHANGE_API_KEY，多货币换算将降级为只使用本地缓存（若无缓存则不转换）。")
+
     application = Application.builder().token(TELEGRAM_TOKEN).build()
 
     async def post_init(app: Application):

requirements.txt

@@ -0,0 +1,7 @@
+python-telegram-bot>=20.0
+pandas
+matplotlib
+python-dateutil
+dateparser
+python-dotenv
+requests