feat: fix vite url using env var

frontend/src/utils/BlogList.tsx

@@ -1,9 +1,10 @@
 import { useState, useEffect } from "react";
+import { API_URL } from "./constants";
 
 export function BlogList() {
   const [content, setContent] = useState("");
   useEffect(() => {
-    fetch(`localhost:8000/get-blogs`)
+    fetch(`${API_URL}/get-blogs`)
       .then((res) => res.text())
       .then(setContent);
   }, []);