docs: update demo link note in README.md to clarify reliance on free services

Author: whiteSHADOW1234

README.md

@@ -13,7 +13,7 @@ A full-stack web application for ordering coffee beans, with a modern tech stack
   <a href="https://coffeebeancart.onrender.com/">Demo Link</a>
 </p>
 
-*Note: The demo link uses Render's free plan, which may go offline occasionally. If it's down, please wait a moment and refresh.*
+*Note: The demo link uses Render's free plan and relies on other free online database hosting services, which may cause the website to go offline occasionally. If it's down, please wait a moment and refresh.*
 
 ## Features